feat: add Codex agent conversion and install support (#362)

Adds Codex as a conversion/install target: each agent → `~/.codex/agents/<slug>.toml` with the three required Codex fields (name, description, developer_instructions).

Validated: all 184 agents generate valid, parseable TOML (incl. 21k-char agents with embedded code blocks) via the PR's TOML basic-string escaper. Matches OpenAI's documented custom-agent schema.

Thanks @yunuskilicdev.

integrations/README.md

@@ -16,6 +16,7 @@ supported agentic coding tools.
 - **[Windsurf](#windsurf)** — `.windsurfrules` in `windsurf/`
 - **[Kimi Code](#kimi-code)** — YAML agent specs in `kimi/`
 - **[Qwen Code](#qwen-code)** — project-scoped `.md` SubAgents in `.qwen/agents/`
+- **[Codex](#codex)** — `.toml` custom agents in `codex/`
 
 ## Quick Install
 
@@ -28,6 +29,7 @@ supported agentic coding tools.
 ./scripts/install.sh --tool copilot
 ./scripts/install.sh --tool openclaw
 ./scripts/install.sh --tool claude-code
+./scripts/install.sh --tool codex
 
 # Gemini CLI needs generated integration files on a fresh clone
 ./scripts/convert.sh --tool gemini-cli
@@ -238,3 +240,20 @@ cd /your/project && /path/to/agency-agents/scripts/install.sh --tool qwen
 ```
 
 See [qwen/README.md](qwen/README.md) for details.
+
+---
+
+## Codex
+
+Each agent is converted into a standalone Codex custom agent TOML file and
+installed to `~/.codex/agents/`.
+
+Because Codex uses generated TOML files rather than the source Markdown
+directly, run the converter before installing from a fresh clone:
+
+```bash
+./scripts/convert.sh --tool codex
+./scripts/install.sh --tool codex
+```
+
+See [codex/README.md](codex/README.md) for details.