feat(skills): add code-wiki skill — closes #486 (#32240)

* feat(skills): add code-wiki skill — closes #486

Bundled skill at skills/software-development/code-wiki/ that generates
comprehensive documentation for any codebase: project overview, architecture
walkthrough with Mermaid flowchart, per-module deep-dives, class diagram,
sequence diagrams, getting-started guide, and (when applicable) API reference.

Output defaults to ~/.hermes/wikis/<repo-name>/ (external to repo, like
Google CodeWiki); in-repo output supported when user explicitly requests it.

Uses only existing Hermes tools (terminal, read_file, search_files,
write_file) — no Docker, no external services, no extra dependencies. Works
on local repos and GitHub URLs (shallow-clones to a temp dir). Bounded scope
defaults (depth 3, cap 10 modules) keep token cost reasonable on large repos.

* refactor(skills): move code-wiki to optional-skills

Per the 'when in doubt, optional' rule — wiki generation is a 'I want this
big thing right now' capability, not daily-driver behavior. Lines up with
finance/research/blockchain skills as install-on-demand rather than always
loaded.

Install via: hermes skills install official/software-development/code-wiki

website/docs/reference/optional-skills-catalog.md

@@ -185,6 +185,7 @@ hermes skills uninstall <skill-name>
 
 | Skill | Description |
 |-------|-------------|
+| [**code-wiki**](/user-guide/skills/optional/software-development/software-development-code-wiki) | Generate wiki docs + Mermaid diagrams for any codebase. |
 | [**rest-graphql-debug**](/user-guide/skills/optional/software-development/software-development-rest-graphql-debug) | Debug REST/GraphQL APIs: status codes, auth, schemas, repro. |
 
 ## web-development