fix: harden A2A recovery e2e flows

[guima-why]

Summary

• Harden A2A pipeline recovery around waiting input, interrupts, rollback, cancellation, and backup-committed snapshot repair.
• Forward rollback reasons back into the target step so Step1 can re-enter the agent loop with the actual changed requirement instead of only seeing a control prompt.
• Expand recovery e2e coverage, including image, rollback, cleanup, deterministic fault injection, and final-target evidence checks.
• Internationalize the new user-visible rollback feedback prefix and update the configured locale catalogs.

Root Cause

Rollback recovery could restart the target step with only a generic continue/control message. In the rollback-step2 flow, Step1 no longer saw the changed user requirement and could complete with the wrong intent. Separately, terminal publication and cancellation races could leave A2A recovery state stale around active interrupts and backup-committed events.

Validation

• make translate
• uv run pytest tests/pipeline/engine/test_pipeline_runner_interrupt.py::TestRollbackContextPropagation tests/pipeline/engine/test_pipeline_runner.py::test_step_rollback_forwards_reason_to_target_step -q → 18 passed
• uv run ruff check src/iac_code/pipeline/engine/pipeline_runner.py tests/pipeline/engine/test_pipeline_runner_interrupt.py
• make test → 8620 passed, 1 skipped, 271 warnings
• make lint → ruff passed, ty passed
• Real A2A recovery matrix: 26/26 PASS at /var/folders/mj/nr6v3rsj3qs6sb6g27lf9zr80000gn/T/iac-code-a2a-e2e-runs/post-fix-full-matrix-20260710T001540Z
• Deterministic fault-after-snapshot: PASS at /var/folders/mj/nr6v3rsj3qs6sb6g27lf9zr80000gn/T/iac-code-a2a-e2e-runs/post-fix-fault-after-snapshot-20260710T022226Z