Add concept list command

[schultzjack]

Linked Issue

Closes OpenConceptLab/ocl_issues#2456

Summary

Adds ocl concept list as a discoverable browse command for concepts. It reuses the existing concept search path with no query, so options like --owner, --repo, --repo-type, pagination, filtering, and --verbose behave the same as ocl concept search.

Also updates the README and demo docs so the new command is visible in the command reference and agent-readiness examples.

Test Plan

• .venv/bin/python -m pytest
• .venv/bin/ruff check src/ocl_cli/commands/concept.py tests/test_concept_commands.py

Notes

I also ran .venv/bin/ruff check .; it currently reports existing lint findings in untouched files, mostly import ordering and unused imports. I kept this PR scoped to concept list rather than mixing in repository-wide lint cleanup.

[schultzjack]

Marked this ready for review. It's been open a couple weeks — flagging in case it fell off the radar. Happy to adjust the approach if this isn't the direction you'd want, or if it's not a priority right now, let me know and I'll focus elsewhere. No rush either way.

[paynejd]

Approving — this closes #2456 exactly as specified. Clean delegation via the shared _search_concepts() helper, includes a test, and updates both the README and demo docs. Thanks @schultzjack, and sorry for the wait on this one.