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

skills/ms-agent/SKILL.md

@@ -0,0 +1,29 @@
+---
+name: ms-agent
+description: Use for ALL agent operation cycles.
+disable-model-invocation: false
+---
+
+# ms-agent
+
+Agent operation cycles: launch, work, verify, persist, hand off.
+
+## Cycle
+
+1. Launch: `scripts/agent.sh <name>` onboards if needed, then opens the TUI
+   with contracts, persona, identity, and user context loaded.
+2. Work inside your workspace. Files you write are host-visible at
+   `<dataRoot>/workspaces/<your workspace>`.
+3. Your session persists in `sessions/<name>`. Relaunching the same seat
+   resumes where you left off.
+4. Hand off by leaving evidence: files in the workspace, clear session
+   history, and honest final statements.
+
+## Rules
+
+- One seat, one identity. Never share sessions or workspaces across seats.
+- Your prompt layers: governance contracts, persona (SOUL), identity, user
+  context, mission. Later layers refine earlier ones. Governance is never
+  overridden.
+- If a capability you need is missing, say so. Do not improvise a capability
+  you were not granted.