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/bash.md

@@ -11,8 +11,8 @@ description: >-
 Extends [`coding-dev.md`](skills-public/coding-dev.md). Everything there applies; this adds shell specifics.
 
 Bash is for **orchestration** — sequencing tools, wiring a build pipeline, gluing CLIs.
-Once a script grows real data structures, arithmetic, or parsing, it wants to be Python or
-a compiled tool instead.
+Once a script grows real data structures, arithmetic, or parsing, it wants to be
+[Python](skills-public/code-languages/python.md) or a compiled tool instead.
 
 ---
 
@@ -165,11 +165,3 @@ Standalone utility scripts belong in a **dedicated, version-controlled scripts d
 symlinked into `PATH` rather than copied there. Never write a loose script directly into
 `~/.local/bin` or another `PATH` directory — the source of truth should be one versioned
 location. See [`cli-tooling.md` §5](skills-public/cli-tooling.md) for the reasoning and the pattern.
-
----
-
-## 10. Related
-- [`coding-dev.md`](skills-public/coding-dev.md) — the general rules this extends.
-- [`cli-tooling.md`](skills-public/cli-tooling.md) — invoking other tools *from* these scripts:
-  discovery, non-interactive flags, structured output.
-- [`python.md`](skills-public/code-languages/python.md) — where a shell script should have become a Python script.