fix: repair broken skill references, fence nesting, and invisible unicode (#2568)

While implementing the Agent Plugin v1 spec in https://github.com/stbenjam/skillsaw/pull/483, I used this repository as a canonical real-world source for tests. Along the way its checks surfaced genuine correctness issues worth fixing regardless of tooling:

- Internal links that do not resolve (22): wrong relative paths, links whose targets are runtime output paths rather than bundled files (now inline code), a schemeless external URL parsed as a relative path, and links to files that do not exist (removed).

- Bundled skill files never referenced from their SKILL.md (14): each is now cited from the section where it is used, so nothing ships unreachable from the skill's instructions.

- Unclosed or mis-nested code fences (11): markdown templates embedding code blocks now use four-backtick outer fences so inner fences nest instead of closing the template early and leaking example content as live markdown; also removed stray orphan fences and closed an unterminated block at end of file.

- Invisible unicode (1): removed a zero-width space from a code example, a copy-paste artifact invisible to reviewers.

skills/azure-deployment-preflight/references/REPORT-TEMPLATE.md

@@ -6,7 +6,7 @@ Use this template structure when generating `preflight-report.md` in the project
 
 ## Template
 
-```markdown
+````markdown
 # Azure Deployment Preflight Report
 
 **Generated:** {timestamp}
@@ -196,7 +196,7 @@ Please resolve the issues listed above before deploying. After fixes:
 ---
 
 *Report generated by Azure Deployment Preflight Skill*
-```
+````
 
 ---
 
@@ -223,7 +223,7 @@ Please resolve the issues listed above before deploying. After fixes:
 
 ## Example Report
 
-```markdown
+````markdown
 # Azure Deployment Preflight Report
 
 **Generated:** 2026-01-16T14:32:00Z
@@ -338,7 +338,7 @@ azd provision --environment dev
 ---
 
 *Report generated by Azure Deployment Preflight Skill*
-```
+````
 
 ---