Fix workspace retry recovery loop

[eshulman2]

Summary

• recreate an existing worker workspace from the fork branch when workspace sync fails
• persist a blocked/paused state when auto-retry reaches the cap to avoid repeated error loops
• add regression coverage for workspace recreation and retry-cap blocking

Tests

• UV_CACHE_DIR=/tmp/uv-cache uv run pytest tests/unit/workflow/nodes/test_workspace_setup.py tests/unit/workflow/test_implement_review.py tests/unit/orchestrator/test_worker.py::TestQuestionDetection::test_auto_retry_cap_marks_workflow_blocked_once
• UV_CACHE_DIR=/tmp/uv-cache uv run ruff check src/forge/workflow/nodes/workspace_setup.py tests/unit/workflow/nodes/test_workspace_setup.py