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

.cursor/hooks/adapter.js

@@ -0,0 +1,62 @@
+#!/usr/bin/env node
+/**
+ * Cursor-to-Claude Code Hook Adapter
+ * Transforms Cursor stdin JSON to Claude Code hook format,
+ * then delegates to existing scripts/hooks/*.js
+ */
+
+const { execFileSync } = require('child_process');
+const path = require('path');
+
+const MAX_STDIN = 1024 * 1024;
+
+function readStdin() {
+  return new Promise((resolve) => {
+    let data = '';
+    process.stdin.setEncoding('utf8');
+    process.stdin.on('data', chunk => {
+      if (data.length < MAX_STDIN) data += chunk.substring(0, MAX_STDIN - data.length);
+    });
+    process.stdin.on('end', () => resolve(data));
+  });
+}
+
+function getPluginRoot() {
+  return path.resolve(__dirname, '..', '..');
+}
+
+function transformToClaude(cursorInput, overrides = {}) {
+  return {
+    tool_input: {
+      command: cursorInput.command || cursorInput.args?.command || '',
+      file_path: cursorInput.path || cursorInput.file || '',
+      ...overrides.tool_input,
+    },
+    tool_output: {
+      output: cursorInput.output || cursorInput.result || '',
+      ...overrides.tool_output,
+    },
+    _cursor: {
+      conversation_id: cursorInput.conversation_id,
+      hook_event_name: cursorInput.hook_event_name,
+      workspace_roots: cursorInput.workspace_roots,
+      model: cursorInput.model,
+    },
+  };
+}
+
+function runExistingHook(scriptName, stdinData) {
+  const scriptPath = path.join(getPluginRoot(), 'scripts', 'hooks', scriptName);
+  try {
+    execFileSync('node', [scriptPath], {
+      input: typeof stdinData === 'string' ? stdinData : JSON.stringify(stdinData),
+      stdio: ['pipe', 'pipe', 'pipe'],
+      timeout: 15000,
+      cwd: process.cwd(),
+    });
+  } catch (e) {
+    if (e.status === 2) process.exit(2); // Forward blocking exit code
+  }
+}
+
+module.exports = { readStdin, getPluginRoot, transformToClaude, runExistingHook };