v2.0.0-rc.2

v2.0.0-rc.2: release candidate — supersedes rc.1

Bundles beta.5..beta.20 + the .gitkeep CI fix.

Net additions over rc.1:
- beta.18 — M1 mobile (PersonaPill compact on <640px)
- beta.19 — OpenAPI sweep tool + initial drift report
- beta.20 — drift fixes (B10 error detail + nil guard, B11/B12 spec align)
- a1600c2 — track internal/web/dist/.gitkeep so go vet does not fail in fresh CI

Live verified at v2.0.0-beta.20 (commit 4919d36). One known issue:
B10b — /var/lib/basement/syncs directory missing on server causes
/user/syncs to 500 even with the detail-improved handler. Cosmetic
followup (no UI feature blocks on it; sync store is opt-in).