Spawn codex agent.

⛰️ Features

• (cli) Spawn codex agent (#631)
• (cli) Route update through the JSON output layer (#620)
• (cli) JSON output layer with a uniform error envelope (#610)
• (server-tools) Built-in web_fetch tool (BYOK) (#612)
• (server-tools) Add Tavily web_search backend, drop Perplexity (#608)
• (server-tools) Built-in web_search with BYOK backends (#603)
• (update) Add bitrouter update self-updater (#607)

🐛 Bug Fixes

• (codex) Harden Codex spawn checks (#632)
• (config) Don't expand ${VAR} inside YAML comments (#609)
• (observe) Stop the settle span double-counting as a telemetry event (#605)

📚 Documentation

• Align docs with current CLI (#637)

⚙️ Miscellaneous Tasks

• Migrate registry into OSS dist (#636)