emrg: add re-trigger-ci.sh — workflow_dispatch CI re-trigger, replaces empty commits

[argszero]

Summary

Completes the host-side symmetry of #527 (which added workflow_dispatch to test.yml). When Actions outages drop push events entirely, the old empty-commit re-trigger (emrg: re-trigger CI (runner cancellation)) both pollutes git history AND depends on the same broken push-event pipeline. The dispatch path (gh workflow run test.yml --ref <branch>) is API-triggered and bypasses it.

Changes

• scripts/re-trigger-ci.sh (new, executable): one-click re-trigger — scripts/re-trigger-ci.sh [branch] (default: current branch) → gh workflow run test.yml --ref <branch>.
• Agent.md: CI section documents the re-trigger command and why (dispatch vs empty-commit).

Verified

• Script works live: ./scripts/re-trigger-ci.sh dispatched Test on master (run 31127604687 created immediately, now queued — dispatch path confirmed functional, matching emrg: add workflow_dispatch to Test workflow — manual CI re-trigger without empty commits #527 evidence).
• bash -n syntax OK; pytest 495 passed (doc-count guard unaffected — no count changes).

[argszero]

✅ LGTM — cycle 20260807-042442 (emrg-00c41753, author self-check, 1/3)

Verified: (1) the script dispatches correctly — ran it live, gh workflow run test.yml --ref master created run 31127604687 immediately (dispatch path functional, matching #527 evidence); (2) bash syntax OK (bash -n); (3) doc-count guard unaffected (pytest 495, GUI 88 counts untouched — Agent.md addition is a CI note, no count drift); (4) completes #527's host-side symmetry (#467-471 lesson: CI capability → documented one-click host command). Pattern: 2 files, +17/-0.

[argszero]

✅ LGTM — cycle 20260807-042518 (emrg-00c41753, 2/3)

Diff verified: new executable scripts/re-trigger-ci.sh (16 lines, set -euo pipefail, default current branch via git rev-parse --abbrev-ref HEAD) + Agent.md CI-section doc line. Host-side symmetry completion of #527 — the one-click dispatch path replaces empty-commit re-triggers that depend on the same broken push pipeline. bash -n syntax OK; doc-count guard passes (2 passed); no test-count impact. mergeable_state=clean.

[argszero]

✅ LGTM — cycle 20260807-043315 (emrg-00c41753, 3/3)

Head 4bdc635 unchanged; diff confirmed (scripts/re-trigger-ci.sh 16 lines + Agent.md doc line). Syntax + doc-count guard verified in prior cycles. mergeable_state=clean. Ready to merge.