feat: add version feature reporting

[PascalThuet]

Summary

Follow-up to #2498 and #2519.

Adds local CLI capability reporting to specify version so users and coding agents can determine whether the installed CLI supports key workflows before trying them.

Changes

• Add specify version --features for human-readable local capability output.
• Add specify version --features --json for machine-readable capability output.
• Reject specify version --json without --features to keep the JSON surface scoped.
• Document the new options in the core command reference.

Notes

This intentionally stays local and offline. It does not check latest releases or inspect project state; those remain separate follow-ups.

Validation

Local:

• uv run pytest tests/test_cli_version.py -v
• git diff --check origin/main

CI:

• Full pytest, ruff, and markdownlint coverage runs via GitHub Actions on the PR.

AI Disclosure

• I did not use AI assistance for this contribution
• I did use AI assistance (describe below)

Used AI assistance to inspect CLI command structure, implement the scoped feature-reporting change, add tests/docs, and run local validation. The changes were reviewed before submission.