Add test-gap-audit and docs-sync-audit skills (#2951)

* feat(skills): add test-gap-audit and docs-sync-audit

Two repo-agnostic review skills that answer questions the existing testing and
documentation skills do not.

test-gap-audit asks which behaviour is not covered, rather than how to write a
test in a given framework. Given no scope it audits the whole repository,
inventories the testable surfaces, and reports which routes, services, jobs and
contracts have no tests, too few assertions, or only indirect coverage. It
bundles coverage_map.py, which detects the test framework and naming convention,
then matches every source file to tests by name, by mirrored path, and by what
the test files actually import, and ranks the unmatched by risk keyword and size.

docs-sync-audit compares what the docs claim against what the code does. It
bundles docs_drift.py, which checks documented npm scripts and make targets
against the ones that exist, relative Markdown links against the filesystem, and
environment variable names in both directions. It also reports a documented
setting that is read only inside a module nothing imports, which is configuration
that reads as working but cannot take effect.

Both are read-only: they report and do not edit unless asked. Both emit the same
contract, so a finding always carries a P0-P3 severity and a path:line you can
open. Both scripts are Python standard library only, install nothing, and are
accelerators rather than requirements, so each skill still works when the script
cannot run.

The existing testing and docs skills here are framework-specific, which is where
most of the value is. These are the repo-agnostic complement: pytest-coverage
raises coverage inside a pytest project, and this decides where coverage is
missing across a repository regardless of language.

* fix: satisfy codespell and regenerate all generated docs

Two CI failures on the first push.

codespell flagged `testng` and `shouldBe` in coverage_map.py. Both are
legitimate identifiers rather than typos: TestNG is the Java test framework the
script detects by name, and shouldBe is the Kotlin and Scala assertion method
matched by its assertion-detection regex. Added both to ignore-words-list with a
comment each, following the convention already used for the other entries.

validate-readme failed because I had reverted docs/README.agents.md. `npm start`
rewrites a Dynatrace MCP URL there from re-fetched external plugin data, which is
unrelated to these skills, so I had excluded it to keep the diff scoped. That was
wrong: the check regenerates every generated file and compares, so the commit has
to carry whatever the build produces. Restored.

---------

Co-authored-by: Aaron Powell <me@aaron-powell.com>

docs/README.skills.md

@@ -163,6 +163,7 @@ See [CONTRIBUTING.md](../CONTRIBUTING.md#adding-skills) for guidelines on how to
 | [devops-rollout-plan](../skills/devops-rollout-plan/SKILL.md)<br />`gh skills install github/awesome-copilot devops-rollout-plan` | Generate comprehensive rollout plans with preflight checks, step-by-step deployment, verification signals, rollback procedures, and communication plans for infrastructure and application changes | None |
 | [diagnose](../skills/diagnose/SKILL.md)<br />`gh skills install github/awesome-copilot diagnose` | Perform a systematic diagnostic scan of an AI workflow across 5 quality dimensions — prompt quality, context efficiency, tool health, architecture fitness, and safety — producing a scored report with prioritized remediation actions. | None |
 | [doc-and-modernize](../skills/doc-and-modernize/SKILL.md)<br />`gh skills install github/awesome-copilot doc-and-modernize` | Two related workflows for a locally-cloned codebase, in one skill. Documentation mode produces a single, comprehensive, verifiable architecture document primarily by reading files on disk (local-first) — use it whenever the user wants to understand, map, document, research, or onboard onto a codebase ("research this repo", "write up the architecture", "do an architecture deep dive", "document how this codebase works", "map the system design", "create an onboarding doc"). Modernization mode generates a phased plan to modernize, migrate, upgrade, or rewrite a legacy system ("modernize this", "plan the migration", "how would we rewrite this", "how do we get off this legacy stack"); if no architecture document exists yet it first runs Documentation mode, then continues straight through to the plan. It assumes the legacy stack may be dead, runs a time-boxed feasibility spike, and picks the highest achievable rung on a safety ladder instead of demanding a fully-green legacy CI gate up front. | `references/copilot-instructions.template.md`<br />`references/migration-hazards.md` |
+| [docs-sync-audit](../skills/docs-sync-audit/SKILL.md)<br />`gh skills install github/awesome-copilot docs-sync-audit` | Run a read-only documentation drift audit for a feature, PR, branch, release, API, configuration change, workflow, CLI, package, or repository area. Use when the user asks whether docs are stale, missing, inconsistent with code, or need updates after code changes. Checks README files, setup guides, API docs, env docs, changelogs, examples, comments, generated docs, and user-facing instructions. This is not a general code review; it compares what the docs claim against what the code does. | `scripts/docs_drift.py` |
 | [documentation-writer](../skills/documentation-writer/SKILL.md)<br />`gh skills install github/awesome-copilot documentation-writer` | Diátaxis Documentation Expert. An expert technical writer specializing in creating high-quality software documentation, guided by the principles and structure of the Diátaxis technical documentation authoring framework. | None |
 | [dotnet-best-practices](../skills/dotnet-best-practices/SKILL.md)<br />`gh skills install github/awesome-copilot dotnet-best-practices` | Ensure .NET/C# code meets best practices for the solution/project. | None |
 | [dotnet-design-pattern-review](../skills/dotnet-design-pattern-review/SKILL.md)<br />`gh skills install github/awesome-copilot dotnet-design-pattern-review` | Review the C#/.NET code for design pattern implementation and suggest improvements. | None |
@@ -410,6 +411,7 @@ See [CONTRIBUTING.md](../CONTRIBUTING.md#adding-skills) for guidelines on how to
 | [technical-job-search](../skills/technical-job-search/SKILL.md)<br />`gh skills install github/awesome-copilot technical-job-search` | Use this skill when a software engineer asks for help with job search tasks: parsing or analyzing a job description, tailoring a CV/resume, writing a cover letter, evaluating a job offer, or drafting a post-interview follow-up email. Do not activate for general career advice unrelated to an active job search action. | None |
 | [technology-stack-blueprint-generator](../skills/technology-stack-blueprint-generator/SKILL.md)<br />`gh skills install github/awesome-copilot technology-stack-blueprint-generator` | Comprehensive technology stack blueprint generator that analyzes codebases to create detailed architectural documentation. Automatically detects technology stacks, programming languages, and implementation patterns across multiple platforms (.NET, Java, JavaScript, React, Python). Generates configurable blueprints with version information, licensing details, usage patterns, coding conventions, and visual diagrams. Provides implementation-ready templates and maintains architectural consistency for guided development. | None |
 | [terraform-azurerm-set-diff-analyzer](../skills/terraform-azurerm-set-diff-analyzer/SKILL.md)<br />`gh skills install github/awesome-copilot terraform-azurerm-set-diff-analyzer` | Analyze Terraform plan JSON output for AzureRM Provider to distinguish between false-positive diffs (order-only changes in Set-type attributes) and actual resource changes. Use when reviewing terraform plan output for Azure resources like Application Gateway, Load Balancer, Firewall, Front Door, NSG, and other resources with Set-type attributes that cause spurious diffs due to internal ordering changes. | `references/azurerm_set_attributes.json`<br />`references/azurerm_set_attributes.md`<br />`scripts/.gitignore`<br />`scripts/README.md`<br />`scripts/analyze_plan.py` |
+| [test-gap-audit](../skills/test-gap-audit/SKILL.md)<br />`gh skills install github/awesome-copilot test-gap-audit` | Run a read-only audit for missing, weak, stale, or mis-scoped test coverage. If the user does not name a scope, audit the full repository and identify important code paths, routes, features, services, workflows, and contracts that lack proper tests. If the user names a feature, PR, branch, route, workflow, service, bug fix, API, security-sensitive path, or risky code change, focus only on that specific scope. Use when the user asks what tests are missing, whether coverage is enough, what regression tests to add, or how to prove a change is safe. This is not a general bug audit and not a security review; it evaluates whether behavior is covered by tests. | `scripts/coverage_map.py` |
 | [threat-model-analyst](../skills/threat-model-analyst/SKILL.md)<br />`gh skills install github/awesome-copilot threat-model-analyst` | Full STRIDE-A threat model analysis and incremental update skill for repositories and systems. Supports two modes: (1) Single analysis — full STRIDE-A threat model of a repository, producing architecture overviews, DFD diagrams, STRIDE-A analysis, prioritized findings, and executive assessments. (2) Incremental analysis — takes a previous threat model report as baseline, compares the codebase at the latest (or a given commit), and produces an updated report with change tracking (new, resolved, still-present threats), STRIDE heatmap, findings diff, and an embedded HTML comparison. Only activate when the user explicitly requests a threat model analysis, incremental update, or invokes /threat-model-analyst directly. | `references/analysis-principles.md`<br />`references/diagram-conventions.md`<br />`references/incremental-orchestrator.md`<br />`references/orchestrator.md`<br />`references/output-formats.md`<br />`references/skeletons/skeleton-architecture.md`<br />`references/skeletons/skeleton-assessment.md`<br />`references/skeletons/skeleton-dfd.md`<br />`references/skeletons/skeleton-findings.md`<br />`references/skeletons/skeleton-incremental-html.md`<br />`references/skeletons/skeleton-inventory.md`<br />`references/skeletons/skeleton-stride-analysis.md`<br />`references/skeletons/skeleton-summary-dfd.md`<br />`references/skeletons/skeleton-threatmodel.md`<br />`references/tmt-element-taxonomy.md`<br />`references/verification-checklist.md` |
 | [tiny-stepping](../skills/tiny-stepping/SKILL.md)<br />`gh skills install github/awesome-copilot tiny-stepping` | Incremental development workflow that makes the smallest meaningful change per step and pauses for feedback, so the direction gets validated early before continuing. Use for careful, iterative implementation with continuous validation. | None |
 | [tldr-prompt](../skills/tldr-prompt/SKILL.md)<br />`gh skills install github/awesome-copilot tldr-prompt` | Create tldr summaries for GitHub Copilot files (prompts, agents, instructions, collections), MCP servers, or documentation from URLs and queries. | None |