feat(#2789): trim skill description anti-patterns; enforce 100-char budget (#2823)

* feat(#2789): trim skill description anti-patterns; enforce 100-char budget

- Trim descriptions in all commands/gsd/*.md files over 100 chars
- Remove flag documentation from descriptions (belongs in argument-hint)
- Remove Triggers: keyword stuffing
- Add scripts/lint-descriptions.cjs — fails on descriptions > 100 chars
- Add npm script: lint:descriptions
- Add tests/enh-2789-description-budget.test.cjs

Closes #2789

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

* docs(#2789): add CHANGELOG entry for description budget lint

* docs(#2789): update COMMANDS.md descriptions; add skill description standards note

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

---------

Co-authored-by: Claude Sonnet 4.6 <noreply@anthropic.com>

package.json

@@ -59,6 +59,7 @@
     "prepublishOnly": "npm run build:hooks && npm run build:sdk",
     "pretest": "npm run build:sdk",
     "pretest:coverage": "npm run build:sdk",
+    "lint:descriptions": "node scripts/lint-descriptions.cjs",
     "lint:tests": "node scripts/lint-no-source-grep.cjs",
     "test": "node scripts/run-tests.cjs",
     "test:coverage": "c8 --check-coverage --lines 70 --reporter text --include 'get-shit-done/bin/lib/*.cjs' --exclude 'tests/**' --all node scripts/run-tests.cjs"