codex: add --type codex to agentapi server #740

Problem

The start_codex() function in start.sh launches agentapi server without --type, so agentapi uses generic terminal output parsing instead of codex-specific status detection.

The module otherwise has full resume support (session tracking, resume <SESSION_ID> subcommand, prompt skipping, continue = true default). This is the only gap.

To verify: inspect the agentapi process args after module startup. --type will be absent.

Desired outcome

• --type codex is passed to agentapi server.
• Expose enable_state_persistence in main.tf (default true) and pass it through to the module "agentapi" block so the Coder UI preserves chat history across restarts, matching the agent's resumed session.

Version bump

patch

Refs #696, coder/internal#1258