Refuse an older Codex by its version, and show which Codex doctor found

[softmarshmallow]

Part (a) of #73. An older codex earlier on PATH broke every Codex call. It rejected codex mcp list --json, so the run was refused with a sentence about MCP servers, and doctor still called the route servable.

What changes

Where	Before	After
A run	Codex's MCP servers could not be listed, so they cannot be turned off	Codex 0.150.0 (from PATH) is older than 0.160.1: update it, or set GRIDA_FX_TOOL_CODEX to a newer one, refused for the whole run before anything else starts
A Codex that prints no version	the same MCP sentence	Codex (from PATH) did not name its version: update it to 0.160.1 or later, or set GRIDA_FX_TOOL_CODEX to a newer one
doctor	route … imagegen@codex servable	a new program codex <path> (PATH, 0.150.0) line, and route … imagegen@codex too old (codex 0.150.0; FX needs 0.160.1+)
doctor <target>	exit 0	exit 1, as a live run would refuse

• The runtime runs codex --version first (30 s). It reads the first X.Y.Z word of the output (codex-cli 0.160.1) and compares it with 0.160.1, the version this behaviour was verified on.
• A refusal names where Codex was found (GRIDA_FX_TOOL_CODEX, PATH or the ChatGPT app), never its path, because refusals are recorded. doctor is terminal output, so it prints the path, as its tool lines already do.
• doctor prints a program line for each program the user installs. Grok Build's line has no version: Grok Build reports it only once started, where it is already checked.
• Shared code: finding a program now also returns where it was found. installed::Version holds the version comparison, which Grok Build's existing check now uses too.
• Spec first: spec/providers.md §9.6 (the version, where Codex was found, the refusals) and §9.8 (where Grok Build was found). The guide (running, Codex), llms.txt, the onboarding reference and AGENT_READINESS follow.

Not included

• Part (b) of Codex: should a newer codex win over an older one earlier on PATH? #73, preferring a newer copy over an older one on PATH. That changes the lookup order, so it is a spec decision, and Codex: should a newer codex win over an older one earlier on PATH? #73 stays open for it.
• Grok Build's version in doctor.

Checks

• cargo fmt --check, cargo clippy --all-targets -- -D warnings
• cargo test --workspace --no-fail-fast: everything passes except two tests that also fail without this change:
  • the Grok dropped-call test fails 2 runs in 3 on main;
  • the host-pool startup test passes on its own.
• New tests:
  • how codex --version output is read;
  • an older Codex is refused for the run and nothing else is started;
  • a Codex that names no version is refused;
  • doctor's program lines and its too old / no version states, including exit 1 for doctor <target>.
• tools/check_spec.py, tools/check_llms.py
• doctor run by hand with a fake old codex placed first on PATH: too old (codex 0.150.0; FX needs 0.160.1+). No live call was made.

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Project	Deployment	Actions	Updated
fx	Ready	Preview	Oct 13, 2026 4:21pm UTC

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