Plan: Make PR-ready waiting requirements unambiguous in agent guidance

Context / Why

The goal is to make both AGENTS.md and .mux/skills/pull-requests/SKILL.md explicitly MUST-level about waiting for PR readiness before declaring work complete. "Ready" must be concretely defined so agents cannot interpret it loosely.

Evidence

• AGENTS.md (## PR Workflow (Codex), lines 95–107): says "stay in this loop until ready" and lists steps, but does not define "ready" or use explicit "MUST NOT finish early" language.
• .mux/skills/pull-requests/SKILL.md:
  • ## CI & Validation (line 34) uses permissive wording: "you may use wait_pr_checks".
  • ### Required Loop Discipline (lines 83–91) says "stay in a review loop until completion" but does not define completion as Codex approval + required CI checks passing.

These are sufficient to justify tightening wording and adding explicit completion gates.

Implementation details

1. Edit AGENTS.md ## PR Workflow (Codex) to define readiness with hard requirements.

   • Add a short "PR readiness is mandatory" block immediately before the loop.
   • Define "ready" as all of the following:
     • Codex has explicitly approved.
     • No unresolved Codex review threads remain.
     • Required CI checks are passing.
   • Add a prohibition: do not claim completion / stop the loop before all conditions are true.

   > PR readiness is mandatory. You MUST keep iterating until the PR is fully ready.
   > A PR is fully ready only when: (1) Codex explicitly approves, (2) all Codex threads are resolved,
   > and (3) all required CI checks pass.
   > You MUST NOT report success or stop the loop before these conditions are met.

2. Edit AGENTS.md loop text to be imperative and unambiguous.

   • Change "stay in this loop until ready" to "you MUST remain in this loop until PR-ready conditions are met".
   • Keep the existing step order; optionally point to ./scripts/wait_pr_ready.sh <pr_number> as the default blocking command when done coding.

   When a PR exists, you MUST remain in this loop until the PR is fully ready:
   ...
   6. After explicit Codex approval, run `./scripts/wait_pr_checks.sh <pr_number>` and wait for required checks to pass.

3. Edit .mux/skills/pull-requests/SKILL.md in ## CI & Validation to distinguish optional vs required waits clearly.

   • Keep guidance that local validation should happen first.
   • Add explicit MUST for final readiness wait:

   - During active iteration, `wait_pr_checks` is optional.
   - Before declaring the PR complete, you MUST wait until required checks pass
     (prefer `./scripts/wait_pr_ready.sh <pr_number>` for Codex+CI end-to-end waiting).

4. Edit .mux/skills/pull-requests/SKILL.md ### Required Loop Discipline to define completion and forbid early stop.

   • Add one normative sentence before the numbered loop that completion is impossible until both Codex approval and required CI pass.
   • Add explicit "MUST NOT" language about responding as done before those conditions.

   Completion criteria are strict: you MUST continue the loop until Codex explicitly approves
   and all required CI checks pass. You MUST NOT mark work complete earlier.

5. Keep the existing narrow early-stop exception, but scope it as an exception to the MUST rule.

   • Retain the misunderstanding clause, but phrase as "only exception" and require pausing for human direction.

Validation approach

• Re-read the edited sections in both files and verify:
  • "MUST" language is present for waiting requirements.
  • "PR-ready" / completion is explicitly defined as Codex approval + CI pass (and thread resolution if included).
  • No contradictory permissive wording remains in those sections.