fix: RPC mode session management not saving sessions

Since version 0.9.0, RPC mode (--mode rpc) was not saving messages to
session files. The agent.subscribe() call with session management logic
was only present in the TUI renderer after it was refactored.

RPC mode now properly saves sessions just like interactive mode.

Added test for RPC mode session management to prevent regression.

Fixes #83

Thanks @kiliman for reporting this issue!

packages/coding-agent/package.json

@@ -1,6 +1,6 @@
 {
 	"name": "@mariozechner/pi-coding-agent",
-	"version": "0.11.1",
+	"version": "0.11.2",
 	"description": "Coding agent CLI with read, bash, edit, write tools and session management",
 	"type": "module",
 	"bin": {
@@ -22,9 +22,9 @@
 		"prepublishOnly": "npm run clean && npm run build"
 	},
 	"dependencies": {
-		"@mariozechner/pi-agent-core": "^0.11.1",
-		"@mariozechner/pi-ai": "^0.11.1",
-		"@mariozechner/pi-tui": "^0.11.1",
+		"@mariozechner/pi-agent-core": "^0.11.2",
+		"@mariozechner/pi-ai": "^0.11.2",
+		"@mariozechner/pi-tui": "^0.11.2",
 		"chalk": "^5.5.0",
 		"diff": "^8.0.2",
 		"glob": "^11.0.3"