feat(coding-agent): add session naming via /name command and extension API

- Add SessionInfoEntry type for session metadata
- Add /name <name> command to set session display name
- Add pi.setSessionName() and pi.getSessionName() extension API
- Session selector shows name (in warning color) instead of first message when set
- Session name included in fuzzy search
- /session command displays name when set

closes #650

packages/coding-agent/src/index.ts

@@ -155,6 +155,7 @@ export {
 	type SessionEntryBase,
 	type SessionHeader,
 	type SessionInfo,
+	type SessionInfoEntry,
 	SessionManager,
 	type SessionMessageEntry,
 	type ThinkingLevelChangeEntry,