Cleanup repo docs and stale local artifacts

[cbusillo]

Summary

• remove the legacy root test wrapper in favor of the documented uv workflow
• align README, contributor, test, release, and agent docs with .github/github-repo-workflow.json
• keep .idea tracked while removing stale settings from its shared project files
• enable the shared IntelliJ inspection profile so tracked IDE inspections are active
• refresh release guidance now that 0.3.0 has been published

Refs #29

Verification

uv sync --locked
uv run pytest
rm -rf dist && uv build
uv run twine check dist/*

CI

• CI passed on f63d29a.
• GitHub has not reported check-runs for latest head yet; local gates above passed on latest head a0f9c4a.

Notes

• .idea remains tracked; its own .idea/.gitignore still handles local workspace state.

[cbusillo]

Temporarily closing and reopening to retrigger pull_request checks on the latest head after GitHub did not create synchronize runs for later branch pushes.