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-file-read/SKILL.md

@@ -0,0 +1,23 @@
+---
+name: ms-file-read
+description: Use this skill when reading any file.
+disable-model-invocation: false
+---
+
+# ms-file-read
+
+Read files before you act on them. Never act on a filename alone.
+
+## Rules
+
+1. Read the file before editing, summarizing, or deciding anything about it.
+2. Large files: read in chunks with offset and limit instead of dumping.
+3. Verify what you read matches what you expected before building on it.
+4. Never read credential material (auth files, tokens, keys). The name is
+   warning enough.
+
+## When
+
+- Before any edit: the edit must match what is actually on disk.
+- Before answering questions about file contents.
+- When a run record, log, or receipt is cited as evidence.