feat: make session creation a sequential workflow

- Refactor CreateSessionForm into step-by-step workflow
- Steps unlock sequentially: Project → Repository → Tool → Clone Mode → Branch
- Add visual step indicators with numbered badges
- Disable controls until prerequisites are met
- Add CSS for workflow step styling

.stoneforge/.gitignore

@@ -0,0 +1,6 @@
+# Runtime data
+*.db
+*.db-journal
+*.db-wal
+*.db-shm
+daemon-state.json