fix(daemon): let a Codex turn ask a structured question

[spacedragon]

What

A codex-acp session could never reach AgentConnect's ACP form elicitation. Everything
between the two ends was already wired — the daemon advertises
elicitation: { form: {}, url: {} } (acp-host.ts), and codex-acp implements
item/tool/requestUserInput → elicitation/create — but Codex itself offers the
request_user_input tool in Default mode only behind the default_mode_request_user_input
feature, which is off by default.

So the model had no such tool. Observed on a real session: it searched its MCP resource
templates, then rg'd the daemon and Codex state directories for a form schema, found
nothing, and answered in prose that interactive forms are unavailable — advising the user
to "switch to Plan mode", which codex-acp does not expose (AgentMode.all() is
read-only / agent / agent-full-access). That advice comes from Codex's own
<collaboration_mode> prompt, which names Default and Plan and says to use the tool
"only when it is listed in the available tools for this turn".

How

• codexConfigWithUserInputTool() in runtimes/codex-config.ts merges the feature into
  CODEX_CONFIG.features one level deep, so it cannot clobber the apps: false /
  memories: false switches other seams set there.
• AcpHost.start() applies it after all caller env is merged, for a Codex runtime, gated on
  opts.onElicit being present — i.e. exactly when this host services session elicitations.
  That gate is host-level, so it excludes an AcpHost built without an answerer (the runtime
  prober, the chat CLI) but NOT the daemon's own background passes, which share an agent's
  host: a distillation / dream / commit-message pass can see the tool, and the coordinator
  declines its request because the pass has no pending turn. Malformed inherited
  CODEX_CONFIG warns and leaves the tool off rather than blocking startup, matching the
  account-app isolation seam above it.
• isCodexRuntimeDef is exported from runtime-defs/executable-hints.ts rather than a
  second copy of the predicate.

Verification

• Driven end to end against a real codex-acp + a minimal ACP client advertising
  elicitation.form, two runs per arm:
  • with the feature → elicitation/create arrives with the full form schema (one field
    per question plus the per-question __other field the console already folds in fix(console): fold a question's own "Other" box into that question #1817).
  • without it → no elicitation; the model emits a markdown pseudo-form.
  • [tools] experimental_request_user_input = { enabled = true } alone → no elicitation.
    That knob is inert in the Codex build bundled with codex-acp@1.10.0 (and is a struct,
    not a bool, so a bare true fails Codex's config parse).
• New tests: three pure-function cases for the merge (including the features-table merge and
  malformed-input rejection) and two AcpHost cases through the env-echo fixture — the tool
  on for an elicitation-servicing host, off for a headless one.
• test/codex-config.test.ts, test/acp-host.test.ts, test/account-apps.test.ts,
  test/elicit-decline-notice.test.ts: 112 passed. Every test file referencing
  CODEX_CONFIG: 182 passed. typecheck / eslint / prettier clean.

Not covered: the webchat card rendering of a Codex-authored form was not exercised against a
live daemon — only the ACP payload was.

[agentconnect-md-test]

No blocking regressions found at 65417351. The feature merge preserves existing config and feature switches, and runs after caller-env assembly and account-app isolation.

Non-blocking clarification: onElicit is a host-level gate, so it does not exclude all background passes as the PR description claims. buildAcpHost() also installs that callback for dream hosts and hosts used by distillation/commit-message passes. Those passes can gain the tool, though the existing missing-pending-turn check safely declines their requests. Narrow the stated headless guarantee accordingly.

Validation: all 112 tests across codex-config, acp-host, account-apps, and elicit-decline-notice passed; daemon typecheck, changed-file ESLint/Prettier, and git diff --check passed. Live webchat rendering was not exercised.

_{sent by review-bot (Codex · gpt-6-astra) · open in session}

[spacedragon]

Fair correction on the headless guarantee — buildAcpHost() does install onElicit for an agent's host, and the background passes share it, so the gate excludes only an AcpHost built without an answerer (prober, chat CLI). PR description narrowed to say exactly that, and to credit the missing-pending-turn check as what actually declines a pass's request. No code change; the comment at the call site already claims only the host-level condition.

[agentconnect-md-test]

That addresses the background-pass clarification. One wording detail: probeCallbacks also supplies a declining onElicit, so the prober isn’t an example of an excluded host.

This remains non-blocking; my approval stands.

_{sent by review-bot (Codex · gpt-6-astra) · open in session}