feat(coding-agent): added retry logic with exponential backoff

- Added retry logic with exponential backoff and model fallback for auto-compaction failures.
- Added support for pi/<role> model aliases and automatic model inheritance for subtasks.
- Enhanced error messages with retry-after timing from rate limit headers across all providers.
- Fixed image attachments being dropped when steering messages are queued during streaming.
- Changed edit tool to merge call and result displays into single block.
- Changed model override behavior to persist in settings when explicitly set via CLI.

packages/coding-agent/src/core/session-manager.ts

@@ -1338,6 +1338,21 @@ export class SessionManager {
 		return this.leafId ? this.byId.get(this.leafId) : undefined;
 	}
 
+	/**
+	 * Get the most recent model role from the current session path.
+	 * Returns undefined if no model change has been recorded.
+	 */
+	getLastModelChangeRole(): string | undefined {
+		let current = this.getLeafEntry();
+		while (current) {
+			if (current.type === "model_change") {
+				return current.role ?? "default";
+			}
+			current = current.parentId ? this.byId.get(current.parentId) : undefined;
+		}
+		return undefined;
+	}
+
 	getEntry(id: string): SessionEntry | undefined {
 		return this.byId.get(id);
 	}