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-builder.ts

@@ -0,0 +1,73 @@
+import { log } from "../../shared/logger"
+import {
+  findEmptyMessages,
+  injectTextPart,
+  replaceEmptyTextParts,
+} from "../session-recovery/storage"
+import type { Client } from "./client"
+
+export const PLACEHOLDER_TEXT = "[user interrupted]"
+
+export function sanitizeEmptyMessagesBeforeSummarize(sessionID: string): number {
+  const emptyMessageIds = findEmptyMessages(sessionID)
+  if (emptyMessageIds.length === 0) {
+    return 0
+  }
+
+  let fixedCount = 0
+  for (const messageID of emptyMessageIds) {
+    const replaced = replaceEmptyTextParts(messageID, PLACEHOLDER_TEXT)
+    if (replaced) {
+      fixedCount++
+    } else {
+      const injected = injectTextPart(sessionID, messageID, PLACEHOLDER_TEXT)
+      if (injected) {
+        fixedCount++
+      }
+    }
+  }
+
+  if (fixedCount > 0) {
+    log("[auto-compact] pre-summarize sanitization fixed empty messages", {
+      sessionID,
+      fixedCount,
+      totalEmpty: emptyMessageIds.length,
+    })
+  }
+
+  return fixedCount
+}
+
+export function formatBytes(bytes: number): string {
+  if (bytes < 1024) return `${bytes}B`
+  if (bytes < 1024 * 1024) return `${(bytes / 1024).toFixed(1)}KB`
+  return `${(bytes / (1024 * 1024)).toFixed(1)}MB`
+}
+
+export async function getLastAssistant(
+  sessionID: string,
+  // eslint-disable-next-line @typescript-eslint/no-explicit-any
+  client: any,
+  directory: string,
+): Promise<Record<string, unknown> | null> {
+  try {
+    const resp = await (client as Client).session.messages({
+      path: { id: sessionID },
+      query: { directory },
+    })
+
+    const data = (resp as { data?: unknown[] }).data
+    if (!Array.isArray(data)) return null
+
+    const reversed = [...data].reverse()
+    const last = reversed.find((m) => {
+      const msg = m as Record<string, unknown>
+      const info = msg.info as Record<string, unknown> | undefined
+      return info?.role === "assistant"
+    })
+    if (!last) return null
+    return (last as { info?: Record<string, unknown> }).info ?? null
+  } catch {
+    return null
+  }
+}