feat: add "blocked for human input" feature across full stack

Agents can now request structured human input when they encounter
genuine blockers (API keys, design choices, external configs). The
request is displayed in the UI with a dynamic form, and the human's
response is stored and made available when the agent resumes.

Changes span 21 files + 1 new component:
- Database: 3 new columns (needs_human_input, human_input_request,
  human_input_response) with migration
- MCP: new feature_request_human_input tool + guards on existing tools
- API: new resolve-human-input endpoint, 4th feature bucket
- Orchestrator: skip needs_human_input features in scheduling
- Progress: 4-tuple return from count_passing_tests
- WebSocket: needs_human_input count in progress messages
- UI: conditional 4th Kanban column, HumanInputForm component,
  amber status indicators, dependency graph support

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

agent.py

@@ -222,7 +222,7 @@ async def run_autonomous_agent(
         # Check if all features are already complete (before starting a new session)
         # Skip this check if running as initializer (needs to create features first)
         if not is_initializer and iteration == 1:
-            passing, in_progress, total = count_passing_tests(project_dir)
+            passing, in_progress, total, _nhi = count_passing_tests(project_dir)
             if total > 0 and passing == total:
                 print("\n" + "=" * 70)
                 print("  ALL FEATURES ALREADY COMPLETE!")
@@ -358,7 +358,7 @@ async def run_autonomous_agent(
             print_progress_summary(project_dir)
 
             # Check if all features are complete - exit gracefully if done
-            passing, in_progress, total = count_passing_tests(project_dir)
+            passing, in_progress, total, _nhi = count_passing_tests(project_dir)
             if total > 0 and passing == total:
                 print("\n" + "=" * 70)
                 print("  ALL FEATURES COMPLETE!")