feat(jobs): push/resume coordinator + /resume (milestone 3)

[shoom1]

Summary

Milestone 3 of phase-2 push/resume (design: docs/plans/2026-06-15-job-push-resume-design.md). Builds on the association layer (#85) and the ADK execution primitive (#86). This closes the loop end to end (ADK): when a finished long-running job opted in (resume_on_complete), the agent is automatically resumed with its result — no polling.

What it adds

Coordinator (cli/app.py) — BaseCLIApp.resume_finished_jobs() drains JobManager.awaiting_resume() into serialized resume turns: one turn at a time via a new self._turn_lock (a user turn and a resume turn never overlap — shared session + thinking boxes), marking each resumed before running so a crash can't double-fire. Called at turn boundaries when job_auto_resume is on, and by /resume on demand (ungated).

Rendering (cli/message_processor.py) — process_resume() streams workflow.resume_with_job_result(record) through the exact same path as a user turn. Factored the shared turn machinery (events box, HITL callback, Ctrl+C cancel, rate-limit retry, token accounting) out of process() into _run_turn(source_factory); process and process_resume are now thin wrappers.

Gating / UX — job_auto_resume setting (default off); /resume command (ResumeCommand); JobMonitor shows ↻N to resume in the status bar when enabled. examples/jobs_demo.py sets job_auto_resume=True to demo it.

Why turn-boundary (not spontaneous mid-idle)

Running a full agent turn's output from a background task while the user sits at the live prompt is display-unsafe (the milestone-2 constraint: thinking_prompt boxes are turn-oriented, add_* prints directly). v1 resumes right after the current/next user turn, plus /resume. The status-bar cue tells the user a resume is waiting. (Spontaneous idle wake is a possible gated v2.)

Testing

• tests/cli/test_resume_coordinator.py — drain resumes each awaiting job once; marks resumed before processing; returns 0 when not ready / no JobManager.
• tests/cli/test_job_monitor.py — ↻N to resume cue shown only when job_auto_resume and there are pending unresumed jobs.
• Live full-loop (tests/integration/test_live_job_resume.py::test_full_resume_loop_via_coordinator, @pytest.mark.llm) — drives the real coordinator: turn 1 starts the job → job finishes → resume_finished_jobs → process_resume → resume_with_job_result → model reacts, rendered into a RecordingSession. Passes.
• Offline suite: 1582 passed, 26 xfailed. The 3 live tests pass against Gemini.

Scope

The coordinator and association layer are backend-agnostic; only resume_with_job_result is ADK-specific so far. LangGraph resume is milestone 5 (update_state with a ToolMessage keyed by call_id). Restart recovery (resuming jobs that finished while the CLI was down) is the remaining milestone-4 item.