feat(release): recursion guard for the health gate; run-task drift warning; M20 packages/* decision recorded (#39)

- release.sh health gate runs with MOSAIC_ENSURE_SKIP=1: the gated task run
  cannot re-enter release self-determination
- run-task.sh warns on release drift instead of silently using a stale image
- ROADMAP: M20 decision recorded (packages/* monorepo at usurpation,
  continuity-first); restructure sequenced as M20 phase 1

Closes #39

docs/SESSIONS.md

@@ -7,3 +7,4 @@ are never rewritten or removed; corrections are new entries.
 | Date (UTC) | Actor | Scope | Outcome / artifacts |
 |---|---|---|---|
 | 2026-09-03 | assistant (conductor + worker) | POC through M12: containerized pi proof, config layer, missions/tasks, release model, adapter seam, workspaces/capabilities, named sessions, retention, session forking, conductor auto-apply, roles/ convention | 13 tags; suites 24/58/14 + 17 conductor + verify green; releases 0.0.1–0.0.7; issues #1–#34 closed |
+| 2026-09-03 | assistant (conductor) | User layer: profile updates (pets, family), ms-user skill review/revision (confirmation rules merged, propose-not-apply, missing-file flow, privacy scope, dispatch = all of user/, rule 9 scratch-file constraint), USER.md.bak removed | skills/ms-user/SKILL.md rewritten; ~/.mosaic-dev/user/USER.md updated (Family, Pets); USER.md.bak deleted |