Add built-in Qoder ACP support

[xinyuan0801]

Summary

• add built-in qoder -> qodercli --acp support and sync the neutral built-in docs surfaces
• add the small Qoder compatibility needed in AcpClient for clean ACP stdio runs and Qoder CLI startup flag forwarding
• persist session options so forwarded Qoder startup flags survive named-session reuse, queue-owner restarts, and session/load recovery
• add regression coverage for registry mapping, client behavior, session persistence, and integration flows

Why

Qoder CLI already supports ACP over stdio, but acpx did not have a built-in entrypoint for it.

Real local ACP smoke also exposed two gaps: Qoder emits benign non-JSON shutdown chatter after successful runs, and Qoder-native startup flags derived from acpx session options would disappear after persistent session reuse unless they were stored in the session record.

This change makes acpx qoder ... work out of the box without adding new generic CLI conventions.

Validation

• pnpm run check
• pnpm run check:docs
• real local qodercli smoke for exec, JSON output, --file, named-session reuse, history, status, set-mode, cancel, --no-wait, approve-reads, and session/load recovery

AI-assisted and fully tested locally.

[xinyuan0801]

@osolmaz could you take a look when you have a chance?

This adds built-in Qoder ACP support plus the small runtime/session persistence compatibility needed for real qodercli flows.

[osolmaz]

Triage result

Human attention: ⚠️ Required
Recommendation: 🏁 escalate to a human
Human decision needed: ready for human landing decision

Quick read

• Solution shape: good enough for the stated feature.
• Conflicts: clean against origin/main at both the initial and final conflict gates.
• Validation: targeted feature validation passed on the PR branch.
• Review: no blocking P0/P1 findings remain.
• CI: green on the current PR head after clearing the workflow approval gate.

Intent

This PR adds first-class built-in Qoder ACP support to acpx so acpx qoder ... works cleanly out of the box and stays documented.

Why

acpx did not recognize Qoder as a built-in ACP agent, and Qoder-specific behavior caused rough edges: benign shutdown text looked like bad JSON, and Qoder startup flags derived from session options were lost when sessions were reused or restored.

Codex review

• Stored GitHub Codex review data contained no blocking feedback for the current head.
• The fresh local Codex review was established successfully and found no P0/P1 issues.
• Remaining non-blocking observations were:
• sessions ensure does not update stored Qoder startup options when it reuses an existing session.
• Empty --allowed-tools currently becomes --allowed-tools= for Qoder.

CI/CD

• The current-head CI workflow run was initially action_required.
• Workflow approval was attempted and succeeded.
• I monitored the rerun through completion, and all jobs passed on the PR head: scope, Format, Typecheck, Lint, Build, Conformance Smoke, Test, and Docs.

Recommendation

This is ready for human landing decision. The implementation is right-shaped for the feature, the conflict gates are clean, targeted validation passed, and CI is green. The remaining Codex notes are P2/P3 and do not block merge unless you want those edge cases tightened before landing.

[osolmaz]

Landed via temp rebase onto main.\n\n- Gate: validation completed for this repo's change scope\n- Land commit: f15d736\n- Merge commit: d5ac799\n\nThanks @xinyuan0801!