refactor(context-window-recovery): split executor and storage into focused modules

Extract recovery strategies and storage management:
- recovery-strategy.ts, aggressive-truncation-strategy.ts
- summarize-retry-strategy.ts, target-token-truncation.ts
- empty-content-recovery.ts, message-builder.ts
- tool-result-storage.ts, storage-paths.ts, state.ts
- client.ts, tool-part-types.ts

src/hooks/anthropic-context-window-limit-recovery/message-storage-directory.ts

@@ -0,0 +1,36 @@
+import { existsSync, readdirSync } from "node:fs"
+import { join } from "node:path"
+
+import { MESSAGE_STORAGE_DIR } from "./storage-paths"
+
+export function getMessageDir(sessionID: string): string {
+	if (!existsSync(MESSAGE_STORAGE_DIR)) return ""
+
+	const directPath = join(MESSAGE_STORAGE_DIR, sessionID)
+	if (existsSync(directPath)) {
+		return directPath
+	}
+
+	for (const directory of readdirSync(MESSAGE_STORAGE_DIR)) {
+		const sessionPath = join(MESSAGE_STORAGE_DIR, directory, sessionID)
+		if (existsSync(sessionPath)) {
+			return sessionPath
+		}
+	}
+
+	return ""
+}
+
+export function getMessageIds(sessionID: string): string[] {
+	const messageDir = getMessageDir(sessionID)
+	if (!messageDir || !existsSync(messageDir)) return []
+
+	const messageIds: string[] = []
+	for (const file of readdirSync(messageDir)) {
+		if (!file.endsWith(".json")) continue
+		const messageId = file.replace(".json", "")
+		messageIds.push(messageId)
+	}
+
+	return messageIds
+}