feat(council-archive): add shared extraction utility and background task type extensions

- Create council-response-extractor.ts with ported extractCouncilResponse()
- Add writeOutputToFile, outputFilePath, _isCompleting to BackgroundTask
- Add writeOutputToFile to LaunchInput
- 8/8 extraction tests passing

src/features/background-agent/types.ts

@@ -63,6 +63,12 @@ export interface BackgroundTask {
   isUnstableAgent?: boolean
   /** Category used for this task (e.g., 'quick', 'visual-engineering') */
   category?: string
+  /** Flag to write raw output to file on completion */
+  writeOutputToFile?: boolean
+  /** Path to the output file after successful write */
+  outputFilePath?: string
+  /** Race condition guard: prevents concurrent re-entry during async completion */
+  _isCompleting?: boolean
 
   /** Last message count for stability detection */
   lastMsgCount?: number
@@ -89,6 +95,8 @@ export interface LaunchInput {
   skillContent?: string
   category?: string
   sessionPermission?: SessionPermissionRule[]
+  /** Flag to write raw output to file on completion */
+  writeOutputToFile?: boolean
 }
 
 export interface ResumeInput {

src/tools/council-archive/council-response-extractor.test.ts

@@ -0,0 +1,103 @@
+import { describe, expect, it } from "bun:test"
+import { extractCouncilResponse } from "./council-response-extractor"
+
+describe("extractCouncilResponse", () => {
+  describe("#given complete COUNCIL_MEMBER_RESPONSE tags", () => {
+    it("#then returns has_response true, response_complete true, and the content", () => {
+      const result = extractCouncilResponse("<COUNCIL_MEMBER_RESPONSE>analysis here</COUNCIL_MEMBER_RESPONSE>")
+
+      expect(result).toEqual({
+        has_response: true,
+        response_complete: true,
+        result: "analysis here",
+      })
+    })
+  })
+
+  describe("#given incomplete tags (opening but no closing)", () => {
+    it("#then returns has_response true, response_complete false, and partial content", () => {
+      const result = extractCouncilResponse("<COUNCIL_MEMBER_RESPONSE>partial analysis")
+
+      expect(result).toEqual({
+        has_response: true,
+        response_complete: false,
+        result: "partial analysis",
+      })
+    })
+  })
+
+  describe("#given missing tags (no opening tag)", () => {
+    it("#then returns has_response false, response_complete false, and null result", () => {
+      const result = extractCouncilResponse("Just some plain text without any tags.")
+
+      expect(result).toEqual({
+        has_response: false,
+        response_complete: false,
+        result: null,
+      })
+    })
+  })
+
+  describe("#given empty content between tags", () => {
+    it("#then returns has_response true, response_complete true, and empty string result", () => {
+      const result = extractCouncilResponse("<COUNCIL_MEMBER_RESPONSE></COUNCIL_MEMBER_RESPONSE>")
+
+      expect(result).toEqual({
+        has_response: true,
+        response_complete: true,
+        result: "",
+      })
+    })
+  })
+
+  describe("#given multiple tag pairs", () => {
+    it("#then returns content from the last opening tag", () => {
+      const text =
+        "<COUNCIL_MEMBER_RESPONSE>first analysis</COUNCIL_MEMBER_RESPONSE>\nSome interim text\n<COUNCIL_MEMBER_RESPONSE>final analysis</COUNCIL_MEMBER_RESPONSE>"
+      const result = extractCouncilResponse(text)
+
+      expect(result).toEqual({
+        has_response: true,
+        response_complete: true,
+        result: "final analysis",
+      })
+    })
+  })
+
+  describe("#given an empty string", () => {
+    it("#then returns has_response false and null result", () => {
+      const result = extractCouncilResponse("")
+
+      expect(result).toEqual({
+        has_response: false,
+        response_complete: false,
+        result: null,
+      })
+    })
+  })
+
+  describe("#given whitespace-only content between tags", () => {
+    it("#then returns has_response true, response_complete true, and empty string result", () => {
+      const result = extractCouncilResponse("<COUNCIL_MEMBER_RESPONSE>   </COUNCIL_MEMBER_RESPONSE>")
+
+      expect(result).toEqual({
+        has_response: true,
+        response_complete: true,
+        result: "",
+      })
+    })
+  })
+
+  describe("#given content with surrounding text before the opening tag", () => {
+    it("#then returns only the tagged content", () => {
+      const text = "Some preamble text\n<COUNCIL_MEMBER_RESPONSE>the actual response</COUNCIL_MEMBER_RESPONSE>"
+      const result = extractCouncilResponse(text)
+
+      expect(result).toEqual({
+        has_response: true,
+        response_complete: true,
+        result: "the actual response",
+      })
+    })
+  })
+})

src/tools/council-archive/council-response-extractor.ts

@@ -0,0 +1,26 @@
+export const OPENING_TAG = "<COUNCIL_MEMBER_RESPONSE>"
+export const CLOSING_TAG = "</COUNCIL_MEMBER_RESPONSE>"
+
+export interface CouncilResponseExtraction {
+  has_response: boolean
+  response_complete: boolean
+  result: string | null
+}
+
+export function extractCouncilResponse(fullText: string): CouncilResponseExtraction {
+  const lastOpenIdx = fullText.lastIndexOf(OPENING_TAG)
+  if (lastOpenIdx === -1) {
+    return { has_response: false, response_complete: false, result: null }
+  }
+
+  const contentStart = lastOpenIdx + OPENING_TAG.length
+  const closingAfterLastOpen = fullText.indexOf(CLOSING_TAG, contentStart)
+
+  if (closingAfterLastOpen === -1) {
+    const partial = fullText.slice(contentStart).trim()
+    return { has_response: true, response_complete: false, result: partial || null }
+  }
+
+  const content = fullText.slice(contentStart, closingAfterLastOpen).trim()
+  return { has_response: true, response_complete: true, result: content }
+}