Route local review feedback through implementation

[eshulman2]

Summary

• make local review read-only and discard accidental reviewer edits
• route failed feature review back to implementation for a dedicated feedback-fix pass
• add implementation prompt and tests for capped review loops across feature and bug workflows

Tests

• uv run pytest tests/unit/workflow/nodes/test_local_reviewer.py tests/unit/workflow/nodes/test_implementation.py tests/unit/workflow/nodes/test_local_review_pass_tracking_errors.py tests/unit/workflow/nodes/test_local_review_status_comments_comprehensive.py tests/flows/bug_workflow/test_complete_bug_flow.py tests/unit/workflow/bug/test_graph.py tests/unit/workflow/feature/test_workflow.py tests/unit/prompts/test_prompt_templates.py -q
• uv run ruff check src/forge/workflow/nodes/local_reviewer.py src/forge/workflow/nodes/implementation.py src/forge/workflow/feature/graph.py src/forge/workflow/feature/state.py src/forge/workflow/bug/graph.py tests/unit/workflow/nodes/test_local_reviewer.py tests/unit/workflow/nodes/test_local_review_pass_tracking_errors.py tests/unit/workflow/nodes/test_local_review_status_comments_comprehensive.py tests/unit/workflow/nodes/test_implementation.py tests/flows/bug_workflow/test_complete_bug_flow.py tests/unit/workflow/bug/test_graph.py tests/unit/workflow/feature/test_workflow.py tests/unit/prompts/test_prompt_templates.py