fix(athena): address 11 audit findings (H2,H3,H5,M1-M4,M8-M11)

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

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

src/tools/council-archive/council-finalize-helpers.ts

@@ -0,0 +1,54 @@
+import { readFile, writeFile, rename } from "node:fs/promises"
+import { join, isAbsolute, resolve, relative } from "node:path"
+import { log } from "../../shared/logger"
+
+export const TASK_ID_PATTERN = /^[a-zA-Z0-9_-]+$/
+
+export function slugify(text: string): string {
+  return text
+    .toLowerCase()
+    .replace(/[^a-z0-9]+/g, "-")
+    .replace(/^-+|-+$/g, "")
+}
+
+export function toPosixPath(pathValue: string): string {
+  return pathValue.replace(/\\/g, "/")
+}
+
+export function extractAgentFromFrontmatter(content: string): string | null {
+  const fmMatch = content.match(/^---\n([\s\S]*?)\n---/)
+  if (!fmMatch) return null
+  const agentLine = fmMatch[1].match(/^agent:\s*(.+)$/m)
+  return agentLine ? agentLine[1].trim() : null
+}
+
+export function isPathEscaping(expectedRoot: string, targetPath: string): boolean {
+  const rel = relative(expectedRoot, targetPath)
+  return rel.startsWith("..") || isAbsolute(rel)
+}
+
+export async function movePromptFile(
+  promptFilePath: string,
+  base: string,
+  absArchiveDir: string,
+  relArchiveDir: string,
+): Promise<string | undefined> {
+  try {
+    const promptFilename = "council-prompt.md"
+    const absPromptSrc = isAbsolute(promptFilePath) ? promptFilePath : resolve(base, promptFilePath)
+    const expectedPromptRoot = join(base, ".sisyphus", "tmp")
+    if (isPathEscaping(expectedPromptRoot, absPromptSrc)) {
+      log("[council-finalize] Rejected prompt_file outside .sisyphus/tmp/", { promptFile: promptFilePath })
+      return undefined
+    }
+    const absPromptDest = join(absArchiveDir, promptFilename)
+    await rename(absPromptSrc, absPromptDest).catch(async () => {
+      const content = await readFile(absPromptSrc, "utf-8")
+      await writeFile(absPromptDest, content, "utf-8")
+    })
+    return toPosixPath(join(relArchiveDir, promptFilename))
+  } catch (err) {
+    log("[council-finalize] Failed to move prompt file", { promptFile: promptFilePath, error: String(err) })
+    return undefined
+  }
+}