codex: add --type codex to agentapi server

[mafredri]

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

[matifali]

@35C4n0r can you take this on?

[mafredri]

The --type codex fix shipped in #781. The enable_state_persistence pass-through was intended to be part of this ticket but not mentioned. Follow-up: #783