Add repo-standardizer skill: polish any GitHub repo surface (#2715)

* Add repo-standardizer skill: polish any GitHub repo surface

* fix(skill): remove non-string metadata and fix template README refs for vally lint

* docs(skill): drop markdown relative links from README language-switcher example

Vally valid-refs flagged ./README.md and ./README.zh.md as missing file
references; they are generated artifacts, not skill files. Keep the
example as plain text to satisfy the linter.

* fix(template): add missing language switcher to English README template

Align with README.zh.md template and SKILL.md switcher convention:
current language as plain text, other languages as relative links.

---------

Co-authored-by: programmingWTF <programmingWTF@users.noreply.github.com>

skills/repo-standardizer/templates/VISION.md

@@ -0,0 +1,32 @@
+# PROJECT_NAME Vision
+
+PROJECT_NAME is <one sentence: what it does and for whom>.
+
+It started as <origin story — one or two sentences>.
+
+## Guiding principles
+
+- <principle 1>
+- <principle 2>
+- <principle 3>
+
+## Current state
+
+- <what exists today>
+
+## Direction
+
+Priority:
+
+- <priority 1>
+- <priority 2>
+
+Next:
+
+- <next 1>
+- <next 2>
+
+Contribution rules:
+
+- One PR = one issue/topic.
+- Commit style: `type(scope): description` (see CONTRIBUTING.md).