Add in-progress status tracking for features

Implements feature locking to prevent multiple agent sessions from working
on the same feature simultaneously. This is essential for parallel agent
execution.

Database changes:
- Add `in_progress` boolean column to Feature model
- Add migration function to handle existing databases

MCP Server tools:
- Add `feature_mark_in_progress` - lock feature when starting work
- Add `feature_clear_in_progress` - unlock feature when abandoning
- Update `feature_get_next` to skip in-progress features
- Update `feature_get_stats` to include in_progress count
- Update `feature_mark_passing` and `feature_skip` to clear in_progress

Backend updates:
- Update progress.py to track and display in_progress count
- Update features router to properly categorize in-progress features
- Update WebSocket to broadcast in_progress in progress updates
- Add in_progress to FeatureResponse schema

Frontend updates:
- Add in_progress to TypeScript types (Feature, ProjectStats, WSProgressMessage)
- Update useWebSocket hook to track in_progress state

Prompt template:
- Add instructions for agents to mark features in-progress immediately
- Document new MCP tools in allowed tools section

Also fixes spec_chat_session.py to use absolute project path instead of
relative path for consistency with CLI behavior.

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

server/services/spec_chat_session.py

@@ -83,8 +83,12 @@ class SpecChatSession:
         except UnicodeDecodeError:
             skill_content = skill_path.read_text(encoding="utf-8", errors="replace")
 
-        # Replace $ARGUMENTS with the project path (use forward slashes for consistency)
-        project_path = f"generations/{self.project_name}"
+        # Ensure project directory exists (like CLI does in start.py)
+        self.project_dir.mkdir(parents=True, exist_ok=True)
+
+        # Replace $ARGUMENTS with absolute project path (like CLI does in start.py:184)
+        # Using absolute path avoids confusion when project folder name differs from app name
+        project_path = str(self.project_dir.resolve())
         system_prompt = skill_content.replace("$ARGUMENTS", project_path)
 
         # Create Claude SDK client with limited tools for spec creation