feat(claude-code): manage commands and skills via home-manager

Add a home-manager module that symlinks config/claude/commands and
config/claude/skills into ~/.claude, mirroring the opencode module.
Seed the commands directory with a /commit slash command.

config/claude/commands/commit.md

@@ -0,0 +1,55 @@
+Create a git commit following the project's conventional commit message conventions.
+
+## Instructions
+
+1. **Check git status and staged changes**:
+   - Run `git status` to see all untracked files
+   - Run `git diff --cached` to see staged changes 
+   - Run `git diff` to see unstaged changes
+
+2. **Stage relevant files**:
+   - Add any untracked files that should be committed
+   - Stage any unstaged changes that should be included
+
+3. **Analyze changes and create commit message**:
+   - Follow the conventional commit format from CLAUDE.md:
+     - `feat:` (new feature for the user)
+     - `fix:` (bug fix for the user)
+     - `docs:` (changes to the documentation)
+     - `style:` (formatting, missing semi colons, etc)
+     - `refactor:` (refactoring production code)
+     - `test:` (adding missing tests, refactoring tests)
+     - `chore:` (updating grunt tasks etc; no production code change)
+   - Write a clear, concise commit message that describes the "why" not just the "what"
+   - Focus on the purpose and impact of the changes
+
+4. **Create the commit**:
+   - Use the conventional commit format
+   - Do not add the Claude Code signature
+
+5. **Verify the commit**:
+   - Run `git status` to confirm the commit succeeded
+   - If pre-commit hooks modify files, amend the commit to include those changes
+
+## Message Format
+
+The commit message should be passed via HEREDOC for proper formatting:
+
+```bash
+git commit -m "$(cat <<'EOF'
+<type>: <description>
+
+<optional body>
+
+EOF
+)"
+```
+
+## Additional Context
+
+Optional commit message details: $ARGUMENTS
+
+**Important**: Never update git config, never use interactive flags like `-i`, and don't push unless explicitly requested.
+
+If the changes are complex, pass enough information for a reviewer in the message body. Reference relevant design documents
+or documentation files, which can help a reviewing AI agent to build enough context for a successful review.