[gpt5-codex-models] feat(models): add GPT-5 Codex presets and model info (low/medium/high)

[just-every-code]

This PR adds first-class support for the new GPT‑5 Codex tiered models (low, medium, high).

Summary of changes

• Core: recognize gpt-5-codex-* in model info with 400k context / 128k max output.
• Common: expose three new built-in model presets so the TUI and MCP server can select them easily:
  • gpt-5-codex-low
  • gpt-5-codex-medium
  • gpt-5-codex-high

Rationale

• Codex CLI now surfaces new GPT‑5 Codex variants; exposing them in code keeps UX parity and lets users pick these tiers directly without manual config.
• Model info ensures sensible defaults for context/max output so token usage displays correctly and compacting thresholds behave as expected.

Validation

• Ran ./build-fast.sh from repo root; build completed cleanly with no warnings or errors.
• Verified presets compile and appear via the shared presets table used by TUI/MCP.

Non-goals

• No changes to workflows, secrets, or CI.
• No behavior changes for existing models.

Closes #169.

Auto-generated for issue #169 by a workflow.
Author: @github-actions[bot]

[github-actions]

Preview Build

You can run this right now! In your terminal just use:

code preview gpt5-codex-models

This will run the version of Code we've created for this issue.

Direct downloads:

• Linux x86_64 (.zst): https://github.com/just-every/code/releases/download/preview-gpt5-codex-models/code-x86_64-unknown-linux-musl.zst
• Linux x86_64 (.tar.gz): https://github.com/just-every/code/releases/download/preview-gpt5-codex-models/code-x86_64-unknown-linux-musl.tar.gz
• Linux aarch64 (.zst): https://github.com/just-every/code/releases/download/preview-gpt5-codex-models/code-aarch64-unknown-linux-musl.zst
• Linux aarch64 (.tar.gz): https://github.com/just-every/code/releases/download/preview-gpt5-codex-models/code-aarch64-unknown-linux-musl.tar.gz
• macOS x86_64 (.zst): https://github.com/just-every/code/releases/download/preview-gpt5-codex-models/code-x86_64-apple-darwin.zst
• macOS x86_64 (.tar.gz): https://github.com/just-every/code/releases/download/preview-gpt5-codex-models/code-x86_64-apple-darwin.tar.gz
• macOS arm64 (.zst): https://github.com/just-every/code/releases/download/preview-gpt5-codex-models/code-aarch64-apple-darwin.zst
• macOS arm64 (.tar.gz): https://github.com/just-every/code/releases/download/preview-gpt5-codex-models/code-aarch64-apple-darwin.tar.gz
• Windows x86_64 (.zip): https://github.com/just-every/code/releases/download/preview-gpt5-codex-models/code-x86_64-pc-windows-msvc.exe.zip

After you run it, please comment here and let me know if it does what you need.