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/js-typescript.md

@@ -175,7 +175,8 @@ Attach an `AbortController` to every long-lived `fetch` and abort it in cleanup.
 ## 10. Tooling & Tests
 
 - Respect the project's runtime and package manager (`npm` / `pnpm` / `yarn` / `bun`) and its
-  lockfile. Do not switch package managers or add a second lockfile.
+  lockfile. Do not switch package managers or add a second lockfile. Build and release scripts
+  around it follow [`bash.md`](skills-public/code-languages/bash.md).
 - Test runner: whatever the project uses (`vitest`, `bun test`, `jest`). Tests live beside the
   code as `*.test.ts(x)` unless the project says otherwise.
 - **Add unit tests for new logic and route tests for new handlers.** Prioritize coverage on
@@ -195,9 +196,3 @@ Attach an `AbortController` to every long-lived `fetch` and abort it in cleanup.
 > current APIs frequently differ from what is in a model's training data. **Read the version's
 > own docs in `node_modules/<pkg>/dist/docs/` or the project's pinned documentation before
 > writing code against them.** Heed deprecation notices rather than pattern-matching from memory.
-
----
-
-## 12. Related
-- [`coding-dev.md`](skills-public/coding-dev.md) — the general rules this extends.
-- [`bash.md`](skills-public/code-languages/bash.md) — for the build/release scripts around these projects.