refactor: split oversized hook.ts to respect 200 LOC limit

- Extract types to types.ts
- Extract constants to constants.ts
- Extract session ID helpers to session-id.ts
- Extract recovery logic to recovery.ts

hook.ts reduced from 331 to 164 LOC

Ultraworked with [Sisyphus](https://github.com/code-yeongyu/oh-my-openagent)

Co-authored-by: Sisyphus <clio-agent@sisyphuslabs.ai>

src/hooks/compaction-context-injector/recovery.ts

@@ -0,0 +1,143 @@
+import { updateSessionAgent } from "../../features/claude-code-session-state"
+import {
+  getCompactionAgentConfigCheckpoint,
+} from "../../shared/compaction-agent-config-checkpoint"
+import { createInternalAgentTextPart } from "../../shared/internal-initiator-marker"
+import { log } from "../../shared/logger"
+import { setSessionModel } from "../../shared/session-model-state"
+import { setSessionTools } from "../../shared/session-tools-store"
+import {
+  createExpectedRecoveryPromptConfig,
+  isPromptConfigRecovered,
+} from "./recovery-prompt-config"
+import {
+  resolveLatestSessionPromptConfig,
+  resolveSessionPromptConfig,
+} from "./session-prompt-config-resolver"
+import { AGENT_RECOVERY_PROMPT, NO_TEXT_TAIL_THRESHOLD, RECOVERY_COOLDOWN_MS, RECENT_COMPACTION_WINDOW_MS } from "./constants"
+import type { CompactionContextClient } from "./types"
+import type { TailMonitorState } from "./tail-monitor"
+
+export function createRecoveryLogic(
+  ctx: CompactionContextClient | undefined,
+  getTailState: (sessionID: string) => TailMonitorState,
+) {
+  const recoverCheckpointedAgentConfig = async (
+    sessionID: string,
+    reason: "session.compacted" | "no-text-tail",
+  ): Promise<boolean> => {
+    if (!ctx) {
+      return false
+    }
+
+    const checkpoint = getCompactionAgentConfigCheckpoint(sessionID)
+    if (!checkpoint?.agent) {
+      return false
+    }
+    const checkpointWithAgent = {
+      ...checkpoint,
+      agent: checkpoint.agent,
+    }
+
+    const tailState = getTailState(sessionID)
+    const now = Date.now()
+    if (tailState.lastRecoveryAt && now - tailState.lastRecoveryAt < RECOVERY_COOLDOWN_MS) {
+      return false
+    }
+
+    const currentPromptConfig = await resolveSessionPromptConfig(ctx, sessionID)
+    const expectedPromptConfig = createExpectedRecoveryPromptConfig(
+      checkpointWithAgent,
+      currentPromptConfig,
+    )
+    const model = expectedPromptConfig.model
+    const tools = expectedPromptConfig.tools
+
+    if (reason === "session.compacted") {
+      const latestPromptConfig = await resolveLatestSessionPromptConfig(ctx, sessionID)
+      if (isPromptConfigRecovered(latestPromptConfig, expectedPromptConfig)) {
+        return false
+      }
+    }
+
+    try {
+      await ctx.client.session.promptAsync({
+        path: { id: sessionID },
+        body: {
+          noReply: true,
+          agent: expectedPromptConfig.agent,
+          ...(model ? { model } : {}),
+          ...(tools ? { tools } : {}),
+          parts: [createInternalAgentTextPart(AGENT_RECOVERY_PROMPT)],
+        },
+        query: { directory: ctx.directory },
+      })
+
+      const recoveredPromptConfig = await resolveLatestSessionPromptConfig(ctx, sessionID)
+      if (!isPromptConfigRecovered(recoveredPromptConfig, expectedPromptConfig)) {
+        log(`[compaction-context-injector] Re-injected agent config but recovery is still incomplete`, {
+          sessionID,
+          reason,
+          agent: expectedPromptConfig.agent,
+          model,
+          hasTools: !!tools,
+          recoveredPromptConfig,
+        })
+        return false
+      }
+
+      updateSessionAgent(sessionID, expectedPromptConfig.agent)
+      if (model) {
+        setSessionModel(sessionID, model)
+      }
+      if (tools) {
+        setSessionTools(sessionID, tools)
+      }
+
+      tailState.lastRecoveryAt = now
+      tailState.consecutiveNoTextMessages = 0
+
+      log(`[compaction-context-injector] Re-injected checkpointed agent config`, {
+        sessionID,
+        reason,
+        agent: expectedPromptConfig.agent,
+        model,
+      })
+
+      return true
+    } catch (error) {
+      log(`[compaction-context-injector] Failed to re-inject checkpointed agent config`, {
+        sessionID,
+        reason,
+        error: String(error),
+      })
+      return false
+    }
+  }
+
+  const maybeWarnAboutNoTextTail = async (sessionID: string): Promise<void> => {
+    const tailState = getTailState(sessionID)
+    if (tailState.consecutiveNoTextMessages < NO_TEXT_TAIL_THRESHOLD) {
+      return
+    }
+
+    const recentlyCompacted =
+      tailState.lastCompactedAt !== undefined &&
+      Date.now() - tailState.lastCompactedAt < RECENT_COMPACTION_WINDOW_MS
+
+    log(`[compaction-context-injector] Detected consecutive assistant messages with no text`, {
+      sessionID,
+      consecutiveNoTextMessages: tailState.consecutiveNoTextMessages,
+      recentlyCompacted,
+    })
+
+    if (recentlyCompacted) {
+      await recoverCheckpointedAgentConfig(sessionID, "no-text-tail")
+    }
+  }
+
+  return {
+    recoverCheckpointedAgentConfig,
+    maybeWarnAboutNoTextTail,
+  }
+}