Add path-scoped .claude/rules

[sudiptob2]

What: Add slash commands (/implement, /address-review, /issue) and extract path-scoped .claude/rules for a more structured Claude Code workflow.

Why: Common tasks like picking up GitHub issues, addressing PR review comments, and drafting issues were manual and repetitive. Testing, config, and version-specific guidance was embedded inline in CLAUDE.md, making it verbose. Extracting rules into path-scoped files surfaces the right context only when editing relevant files.

Changes:

• Add /implement command: fetches a GitHub issue, creates a branch from latest master (with remote selection), plans the work, executes step-by-step with programmer approval, commits incrementally, and generates a PR summary
• Add /address-review command: walks through unaddressed PR review comments one by one (fix, reply, or skip), commits fixes, and posts replies with confirmation
• Add /issue command: drafts a GitHub issue markdown file from user-provided context and saves to plans/
• Extract testing patterns, config entry conventions, and version-specific SparkSubmit rules into .claude/rules/ with path-scoped triggers
• Scope gh CLI permissions in settings.json to specific subcommands instead of a blanket gh * wildcard
• Trim CLAUDE.md by replacing inline code examples with references to the new rule files

How to verify:

1. Run /implement <issue-number> and verify it walks through all 5 phases (fetch, branch, plan, execute, summary)
2. Run /address-review <pr-number> on a PR with review comments
3. Edit a file under src/test/ and confirm testing rules context is surfaced
4. Check .claude/settings.json for scoped gh permissions

[GeorgeJahad]

I haven't had a chance to experiment with all the features but it looks good to me.

Thanks @sudiptob2 !