docs: P2 repo-visibility cleanup — stale CLAUDE.md note, /demo API, PR template

[w7-mgfcode]

P2 items from the GitHub-presence audit:

• D4 — CLAUDE.md Learnings note references [UNVERIFIED] tags in docs/_base/ that no longer exist (only [ASSUMPTION] remains). Stale.
• D9 — README does not document the /demo/run + /demo/stream endpoints shipped in feat(api,ui): in-product demo showcase page #132, though API_CONTRACTS.md does.
• T3 — PR template 'Type of Change' checkboxes don't map cleanly to the commit-format types (feat/fix/chore/docs/refactor/test).

D3 ([ASSUMPTION] compliance tags) and D7 (PRP/INITIAL pairing exception) are left as operator-judgment items.

[w7-mgfcode]

Resolved — merged into dev (PR #145). Auto-close did not fire because the PR targeted dev, not the default branch.