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

.codex/config.toml

@@ -0,0 +1,80 @@
+# Everything Claude Code (ECC) — Codex CLI Reference Configuration
+#
+# Copy this file to ~/.codex/config.toml to apply globally.
+# Or keep it in your project root for project-level config.
+#
+# Docs: https://github.com/openai/codex
+
+# Model selection
+model = "o4-mini"
+model_provider = "openai"
+
+# Permissions
+[permissions]
+# "untrusted" = no writes, "on-request" = ask per action, "never" = full auto
+approval_policy = "on-request"
+# "off", "workspace-read", "workspace-write", "danger-full-access"
+sandbox_mode = "workspace-write"
+
+# Notifications (macOS)
+[notify]
+command = "terminal-notifier -title 'Codex ECC' -message 'Task completed!' -sound default"
+on_complete = true
+
+# History - persistent instructions applied to every session
+[history]
+# These are prepended to every conversation
+persistent_instructions = """
+Follow ECC principles:
+1. Test-Driven Development (TDD) - write tests first, 80%+ coverage required
+2. Immutability - always create new objects, never mutate
+3. Security-First - validate all inputs, no hardcoded secrets
+4. Conventional commits: feat|fix|refactor|docs|test|chore|perf|ci: description
+5. File organization: many small files (200-400 lines, 800 max)
+6. Error handling: handle at every level, never swallow errors
+7. Input validation: schema-based validation at system boundaries
+"""
+
+# MCP Servers
+# Codex supports command-based MCP servers
+[mcp_servers.github]
+command = "npx"
+args = ["-y", "@modelcontextprotocol/server-github"]
+
+[mcp_servers.context7]
+command = "npx"
+args = ["-y", "@upstash/context7-mcp@latest"]
+
+[mcp_servers.memory]
+command = "npx"
+args = ["-y", "@modelcontextprotocol/server-memory"]
+
+[mcp_servers.sequential-thinking]
+command = "npx"
+args = ["-y", "@modelcontextprotocol/server-sequential-thinking"]
+
+# Additional MCP servers (uncomment as needed):
+# [mcp_servers.supabase]
+# command = "npx"
+# args = ["-y", "supabase-mcp-server@latest", "--read-only"]
+#
+# [mcp_servers.firecrawl]
+# command = "npx"
+# args = ["-y", "firecrawl-mcp"]
+#
+# [mcp_servers.railway]
+# command = "npx"
+# args = ["-y", "@anthropic/railway-mcp"]
+
+# Features
+[features]
+web_search_request = true
+
+# Profiles — switch with CODEX_PROFILE=<name>
+[profiles.strict]
+approval_policy = "on-request"
+sandbox_mode = "workspace-read"
+
+[profiles.yolo]
+approval_policy = "never"
+sandbox_mode = "workspace-write"