refactor(skills): inline cross-links, drop Related sections, fix conventions

- all nine files: trailing "Related" sections removed, their unique links
  inlined where the topic actually arises (FFI boundary -> c-cpp, embedded
  frontend -> js-typescript, build scripts -> bash, etc.)
- README conventions: rule 2 mandated a Related Skills section, which now
  contradicts practice — replaced with inline-linking and one-home-per-fact
  rules. The <repo>/<rel path> rule was appended after the wrong section
  last commit; moved into the list where it belongs.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

code-languages/go.md

@@ -135,7 +135,8 @@ CGO_ENABLED=0 go build -trimpath -ldflags="-s -w" -o bin/app ./cmd/app
 - One package per concern; **package names are lowercase, single-word, no underscores**, and
   never `util` or `common`.
 - Keep the exported surface small. Unexported by default.
-- Embed frontend/static assets with `//go:embed` for single-binary distribution.
+- Embed frontend/static assets with `//go:embed` for single-binary distribution — the frontend
+  itself follows [`js-typescript.md`](skills-public/code-languages/js-typescript.md).
 - File and function size limits from the general rules apply.
 
 ---
@@ -149,9 +150,3 @@ CGO_ENABLED=0 go build -trimpath -ldflags="-s -w" -o bin/app ./cmd/app
 - **Regression test every fixed bug.**
 - **Never run destructive operations against real accounts or user data during validation** —
   temporary fixtures only.
-
----
-
-## 10. Related
-- [`coding-dev.md`](skills-public/coding-dev.md) — the general rules this extends.
-- [`js-typescript.md`](skills-public/code-languages/js-typescript.md) — for the embedded frontend in a Go service.