fix(coderabbit): resolve all 12 findings on PR #3152

MAJOR (security/correctness):
- commands/gsd/debug.md: add Write to allowed-tools (session file creation
  requires it — workflow explicitly says 'use Write tool, never heredoc')
- workflows/debug.md: add SLUG sanitization guard to steps 1b+1c (status/
  continue subcommands used raw user input in file paths — path traversal)
- workflows/thread.md: sanitize $ARGUMENTS in RESUME mode before file path
  construction (was bypassing the sanitization guard in CLOSE/STATUS modes)

MINOR (consistency/correctness):
- docs/INVENTORY-MANIFEST.json: remove stale top-level 'workflows' array
  (duplicate of families.workflows introduced in earlier update)
- commands/gsd/resume-work.md: normalize process to 'Execute end-to-end.'
- commands/gsd/settings.md: normalize process to 'Execute end-to-end.'
- commands/gsd/update.md: normalize otherwise branch to 'execute end-to-end.'
- docs/adr/0002: add Status: Accepted + Date header (ADR convention)
- workflows/extract-learnings.md: rename step extract_learnings → extract-learnings
- tests/extract-learnings.test.cjs: tighten step-name assertion to exact name

ARCHITECTURE:
- scripts/command-contract-helpers.cjs: extract CANONICAL_TOOLS, parseFrontmatter,
  executionContextRefs as shared module — single source of truth consumed by
  both lint script and test suite (prevents silent lint/test disagreement)
- scripts/lint-command-contract.cjs: require() helpers instead of duplicating
- tests/command-contract.test.cjs: require() helpers; move readFileSync calls
  inside test() callbacks (registration-time throws surface as named failures)

get-shit-done/workflows/debug.md

@@ -64,6 +64,8 @@ STOP after displaying list. Do NOT proceed to further steps.
 
 When SUBCMD=status and SLUG is set:
 
+**Sanitize SLUG first:** strip whitespace, reject unless it matches `^[a-z0-9][a-z0-9-]*$`, enforce max 30 chars, reject any `..`, `/`, or `\`. If invalid, print "No debug session found with slug: {SLUG}" and stop.
+
 Check `.planning/debug/{SLUG}.md` exists. If not, check `.planning/debug/resolved/{SLUG}.md`. If neither, print "No debug session found with slug: {SLUG}" and stop.
 
 Parse and print full summary:
@@ -81,6 +83,8 @@ No agent spawn. Just information display. STOP after printing.
 
 When SUBCMD=continue and SLUG is set:
 
+**Sanitize SLUG first:** strip whitespace, reject unless it matches `^[a-z0-9][a-z0-9-]*$`, enforce max 30 chars, reject any `..`, `/`, or `\`. If invalid, print "No active debug session found with slug: {SLUG}. Check `/gsd-debug list` for active sessions." and stop.
+
 Check `.planning/debug/{SLUG}.md` exists. If not, print "No active debug session found with slug: {SLUG}. Check `/gsd-debug list` for active sessions." and stop.
 
 Read file and print Current Focus block to console: