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

compose.yaml

@@ -26,6 +26,8 @@ services:
       MOSAIC_AGENT_NAME: ${MOSAIC_AGENT_NAME:-}
       MOSAIC_AGENT_ROLE: ${MOSAIC_AGENT_ROLE:-}
       MOSAIC_AGENT_SOUL_FILE: ${MOSAIC_AGENT_SOUL_FILE:-}
+      # Skill dirs explicitly provided to the seat (M17)
+      MOSAIC_SKILLS: ${MOSAIC_SKILLS:-}
       # mock adapter only: verbatim response for deterministic seam tests
       MOSAIC_MOCK_RESPONSE: ${MOSAIC_MOCK_RESPONSE:-}
       # Documented container auth alternative: provider API key via