fix: support --model for codex sessions

[osolmaz]

Summary

• preserve the core fix from #128: apply Codex --model after session/new via session/set_config_option
• keep the requested model value unchanged instead of rewriting aliases
• include the small landing fixes needed on top of current main

Context

This PR supersedes #128 only because the original fork branch could not be updated from this maintainer environment even though the PR was marked editable.

Original author and core fix: @Asm3r96
Original PR: #128

Validation

• pnpm run check:docs
• focused CLI regression: prompt reconciles agentSessionId from loadSession metadata
• local pnpm run test:coverage and pnpm run check still hit the same repo-local coverage baseline failure seen on main in this environment under the only installed local Node runtime, so they are not useful as change-specific signal here

[osolmaz]

Landed from this replacement branch because the original fork-backed PR #128 could not be updated from the maintainer environment.\n\n- Original author: @Asm3r96\n- Merge commit: 6fc4d65\n\nThanks @Asm3r96!

[chatgpt-codex-connector]

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[chatgpt-codex-connector]

Recognize codex-acp script paths as Codex sessions

isCodexAcpCommand only treats a command as Codex when the basename is exactly codex-acp (with only .cmd/.exe/.bat stripped) or when an argument contains codex-acp. If agents.codex.command is configured to a direct script path like /opt/tools/codex-acp.js with no extra args, this check returns false, so AcpClient.createSession never sends session/set_config_option for model and --model is silently ignored for that Codex setup.

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