fix(coding): close PI-100 review findings

electron/coding-runtime/pi/resource-loader.ts

@@ -1,10 +1,11 @@
-import { mkdir, stat } from 'node:fs/promises';
+import { mkdir, rename, stat } from 'node:fs/promises';
 import path from 'node:path';
 import {
   BUNDLED_CODING_SKILL_IDS,
   type BundledCodingSkillId,
 } from '../../../shared/coding-skills';
 import { atomicWriteJson, atomicWriteText } from '../../coding-projects/atomic-json';
+import { validateSessionKey } from '../../coding-projects/conversation-store';
 import type { PiProviderSelection } from './provider-config';
 import type { PiManagedInputRevision } from './managed-input-revision';
 
@@ -104,6 +105,31 @@ export async function ensurePiManagedPaths(userDataDir: string): Promise<PiManag
   return paths;
 }
 
+export async function archivePiConversationSession(input: {
+  userDataDir: string;
+  projectId: string;
+  sessionKey: string;
+}): Promise<string | null> {
+  const projectId = managedSegment(input.projectId, 'Project id');
+  const sessionKey = validateSessionKey(input.sessionKey);
+  const paths = getPiManagedPaths(input.userDataDir);
+  const source = path.join(paths.sessionsDir, projectId, `${sessionKey}.jsonl`);
+  const targetDirectory = path.join(paths.trashDir, projectId);
+  const target = path.join(targetDirectory, `${sessionKey}.jsonl`);
+  await mkdir(targetDirectory, { recursive: true });
+  try {
+    await rename(source, target);
+    return target;
+  } catch (error) {
+    if ((error as NodeJS.ErrnoException).code !== 'ENOENT') throw error;
+    const alreadyArchived = await stat(target).catch((targetError: NodeJS.ErrnoException) => {
+      if (targetError.code === 'ENOENT') return null;
+      throw targetError;
+    });
+    return alreadyArchived?.isFile() ? target : null;
+  }
+}
+
 function normalizeSkillIds(skillIds: readonly string[]): BundledCodingSkillId[] {
   const result: BundledCodingSkillId[] = [];
   const seen = new Set<string>();