SkillCheck validator, Cursor exports, and per-agent installers (#27)

Three more learnings from alirezarezvani/claude-skills, applied:

1. SkillCheck validator (scripts/skillcheck.mjs) — validates every SKILL.md
   against the authoring standard (frontmatter, name/folder match, trigger +
   produces clauses, required headings) plus tier referential integrity.
   Errors fail CI; --strict fails on warnings too. New skillcheck.yml workflow
   and a SkillCheck status badge in the README. Current: 0 errors / 14 advisory
   warnings across 172 skills.

2. Cursor export platform — build-exports.mjs now generates
   exports/cursor/<bundle>/<skill>/<skill>.mdc rule files. The PLATFORMS
   registry now supports per-skill filenames (file as a function).

3. Per-agent installers — scripts/install.sh unifies install for
   claude/hermes/codex/openclaw/cursor (--link, --target, --dry-run, --list).
   Curl-able one-liners codex-install.sh, openclaw-install.sh, and
   cursor-install.sh clone the library and install in a single command.

README documents the one-line installs and Cursor exports; CHANGELOG and the
authoring standard updated.


Claude-Session: https://claude.ai/code/session_016JWn5jRD5tcEFKrubjQ6Px

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

.github/workflows/skillcheck.yml

@@ -0,0 +1,34 @@
+name: SkillCheck
+
+# Validates every skills/<name>/SKILL.md against the project authoring standard
+# (SKILL-AUTHORING-STANDARD.md). Errors fail the build; warnings are advisory.
+
+on:
+  push:
+    branches: [main]
+    paths:
+      - 'skills/**'
+      - 'skill-tiers.json'
+      - 'scripts/skillcheck.mjs'
+      - '.github/workflows/skillcheck.yml'
+  pull_request:
+    paths:
+      - 'skills/**'
+      - 'skill-tiers.json'
+      - 'scripts/skillcheck.mjs'
+      - '.github/workflows/skillcheck.yml'
+
+jobs:
+  validate:
+    runs-on: ubuntu-latest
+    steps:
+      - name: Checkout
+        uses: actions/checkout@v4
+
+      - name: Set up Node
+        uses: actions/setup-node@v4
+        with:
+          node-version: '20'
+
+      - name: Run SkillCheck
+        run: node scripts/skillcheck.mjs