feat(#789): elevate CodeBuddy — slash commands (#830)

* feat(#789): elevate CodeBuddy — emit slash commands (+ document subagent/MCP scope)

Emit a CodeBuddy slash-command surface so GSD workflows appear in the
'/' menu, reaching parity with other elevated runtimes.

- Add convertClaudeCommandToCodebuddyCommand and register a commands/
  artifact kind for the codebuddy runtime (commands/gsd-<name>.md),
  consistent with the Cursor (#785) and Augment (#790) commands surfaces.
- Mark emitted skills user-invocable:false so the commands surface is the
  sole '/' entry point (no duplicate /gsd-* entries); skills stay
  model-invocable. CodeBuddy's SKILL.md supports this field.
- Normalize $HOME/.codebuddy (bare + slash) path forms in runtime
  rewrites so --config-dir/local installs don't leak the default home.
- Report installed commands/ count on install; uninstall prunes gsd-*
  commands while preserving user-owned commands.

Scope: subagents (~/.codebuddy/agents/) are already emitted by the
generic agents block (unchanged); no mcp.json is written (gsd ships no
MCP server, and CodeBuddy's mcp.json registers only external servers).

Closes #789

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

* chore(#789): set changeset pr number to 830

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

---------

Co-authored-by: Claude Opus 4.8 <noreply@anthropic.com>

docs/ARCHITECTURE.md

@@ -808,7 +808,7 @@ The migration-specific ownership and source snapshots live in
 | Trae | `~/.trae` | `./.trae` | `skills/gsd-*/SKILL.md` | `agents/gsd-*.md` | Rule references under `rules/`; no GSD hooks |
 | Qwen Code | `~/.qwen` | `./.qwen` | `skills/gsd-*/SKILL.md` | `agents/gsd-*.md` | Common GSD settings and hook entries where supported |
 | Hermes Agent | `~/.hermes` | `./.hermes` | `skills/gsd/DESCRIPTION.md` plus `skills/gsd/gsd-*/SKILL.md` | `agents/gsd-*.md` | Common GSD settings and hook entries where supported |
-| CodeBuddy | `~/.codebuddy` | `./.codebuddy` | `skills/gsd-*/SKILL.md` | `agents/gsd-*.md` | Common GSD settings and hook entries where supported |
+| CodeBuddy | `~/.codebuddy` | `./.codebuddy` | `skills/gsd-*/SKILL.md` (`user-invocable: false`) | `agents/gsd-*.md` | `/gsd-*` slash commands under `commands/`; common GSD settings and hook entries where supported |
 | Cline | `~/.cline` | project root | `.clinerules` | Rules only | No GSD hooks or statusline |
 
 ### Upstream Contract Sources