Simplify compaction: remove proactive abort, use Agent.continue() for retry

- Add agentLoopContinue() to pi-ai for resuming from existing context
- Add Agent.continue() method and transport.continue() interface
- Simplify AgentSession compaction to two cases: overflow (auto-retry) and threshold (no retry)
- Remove proactive mid-turn compaction abort
- Merge turn prefix summary into main summary
- Add isCompacting property to AgentSession and RPC state
- Block input during compaction in interactive mode
- Show compaction count on session resume
- Rename RPC.md to rpc.md for consistency

Related to #128

package.json

@@ -34,5 +34,8 @@
 	"engines": {
 		"node": ">=20.0.0"
 	},
-	"version": "0.0.3"
+	"version": "0.0.3",
+	"dependencies": {
+		"get-east-asian-width": "^1.4.0"
+	}
 }