feat: Add mol_type schema field for molecule type classification (bd-oxgi)

Add mol_type field to beads for swarm coordination:
- Values: 'swarm' (multi-polecat), 'patrol' (recurring ops), 'work' (default)
- Nullable, defaults to empty string (treated as 'work')

Changes:
- Add mol_type column to SQLite schema and migration 031
- Add MolType type with IsValid() validation in types.go
- Update insertIssue/GetIssue to handle mol_type
- Add --mol-type flag to create command
- Add mol_type filtering to list and ready commands
- Update RPC protocol for daemon mode support
- Update test schema in migrations_test.go

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

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

internal/storage/sqlite/migrations_test.go

@@ -502,9 +502,10 @@ func TestMigrateContentHashColumn(t *testing.T) {
 				last_activity DATETIME,
 				role_type TEXT DEFAULT '',
 				rig TEXT DEFAULT '',
+				mol_type TEXT DEFAULT '',
 				CHECK ((status = 'closed') = (closed_at IS NOT NULL))
 			);
-			INSERT INTO issues SELECT id, title, description, design, acceptance_criteria, notes, status, priority, issue_type, assignee, estimated_minutes, created_at, '', updated_at, closed_at, external_ref, compaction_level, compacted_at, original_size, compacted_at_commit, source_repo, '', NULL, '', '', '', '', 0, 0, 0, '', '', '', '', '', '', 0, '', '', '', '', NULL, '', '' FROM issues_backup;
+			INSERT INTO issues SELECT id, title, description, design, acceptance_criteria, notes, status, priority, issue_type, assignee, estimated_minutes, created_at, '', updated_at, closed_at, external_ref, compaction_level, compacted_at, original_size, compacted_at_commit, source_repo, '', NULL, '', '', '', '', 0, 0, 0, '', '', '', '', '', '', 0, '', '', '', '', NULL, '', '', '' FROM issues_backup;
 			DROP TABLE issues_backup;
 		`)
 		if err != nil {