Merge develop into main for minor release

[pallyoung]

Summary

• Expand provider runtime support across Codex, Cursor, Gemini, and OpenCode.
• Add agent instructions generation, skills management, and work analysis surfaces.
• Add a minor changeset for @spencer-kit/coder-studio.

Verification

• pnpm ci:verify

Notes

• Recreates the develop-to-main flow after reverting the earlier direct merge on main.
• Confirmed the previously removed six work-analysis docs are not restored in this branch.