feat: add Cursor, Codex, and OpenCode harnesses — maximize every AI coding tool

- AGENTS.md: universal cross-tool file read by Claude Code, Cursor, Codex, and OpenCode
- .cursor/: 15 hook events via hooks.json, 16 hook scripts with DRY adapter pattern,
  29 rules (9 common + 20 language-specific) with Cursor YAML frontmatter
- .codex/: reference config.toml, Codex-specific AGENTS.md supplement,
  10 skills ported to .agents/skills/ with openai.yaml metadata
- .opencode/: 3 new tools (format-code, lint-check, git-summary), 3 new hooks
  (shell.env, experimental.session.compacting, permission.ask), expanded instructions,
  version bumped to 1.6.0
- README: fixed Cursor section, added Codex section, added cross-tool parity table
- install.sh: now copies hooks.json + hooks/ for --target cursor

.opencode/opencode.json

@@ -4,11 +4,19 @@
   "small_model": "anthropic/claude-haiku-4-5",
   "default_agent": "build",
   "instructions": [
+    "AGENTS.md",
     "CONTRIBUTING.md",
     ".opencode/instructions/INSTRUCTIONS.md",
     "skills/tdd-workflow/SKILL.md",
     "skills/security-review/SKILL.md",
-    "skills/coding-standards/SKILL.md"
+    "skills/coding-standards/SKILL.md",
+    "skills/frontend-patterns/SKILL.md",
+    "skills/backend-patterns/SKILL.md",
+    "skills/e2e-testing/SKILL.md",
+    "skills/verification-loop/SKILL.md",
+    "skills/api-design/SKILL.md",
+    "skills/strategic-compact/SKILL.md",
+    "skills/eval-harness/SKILL.md"
   ],
   "plugin": [
     "./.opencode/plugins"