fix: WSL mount path translation + Windows drive letter normalization

Manually ported from upstream:
- c239cda6: translateWslMountPath() converts /mnt/X/... → X:/... on Windows
- 7f5fbdab: normalizeDriveLetter() uppercases drive letter (c:/ → C:/)

Both are no-op on macOS/Linux. Fixes session fragmentation on Windows+WSL.

src/main/utils/metadataExtraction.ts

@@ -9,11 +9,24 @@ import * as readline from 'readline';
 import { LocalFileSystemProvider } from '../services/infrastructure/LocalFileSystemProvider';
 import { type ChatHistoryEntry, isTextContent, type UserEntry } from '../types';
 
+import { translateWslMountPath } from './pathDecoder';
+
 import type { FileSystemProvider } from '../services/infrastructure/FileSystemProvider';
 import type { Readable } from 'stream';
 
 const logger = createLogger('Util:metadataExtraction');
 
+/**
+ * Normalize Windows drive letter to uppercase for consistent path comparison.
+ * CLI uses uppercase (C:\...) while VS Code extension uses lowercase (c:\...).
+ */
+function normalizeDriveLetter(p: string): string {
+  if (p.length >= 2 && p[1] === ':') {
+    return p[0].toUpperCase() + p.slice(1);
+  }
+  return p;
+}
+
 const defaultProvider = new LocalFileSystemProvider();
 
 const JSONL_HEAD_TIMEOUT_MS = 2000;
@@ -100,7 +113,7 @@ export async function extractCwd(
       }
       // Only conversational entries have cwd
       if ('cwd' in entry && entry.cwd) {
-        return entry.cwd;
+        return normalizeDriveLetter(translateWslMountPath(entry.cwd));
       }
     }
   } catch (error) {

src/main/utils/pathDecoder.ts

@@ -69,7 +69,10 @@ export function decodePath(encodedName: string): string {
   }
 
   // Ensure leading slash for POSIX-style absolute paths
-  return decodedPath.startsWith('/') ? decodedPath : `/${decodedPath}`;
+  const absolutePath = decodedPath.startsWith('/') ? decodedPath : `/${decodedPath}`;
+
+  // Translate WSL mount paths to Windows drive-letter paths on Windows
+  return translateWslMountPath(absolutePath);
 }
 
 /**
@@ -91,6 +94,23 @@ export function extractProjectName(encodedName: string, cwdHint?: string): strin
   return segments[segments.length - 1] || encodedName;
 }
 
+/**
+ * Translate WSL mount paths (/mnt/X/...) to Windows drive-letter paths (X:/...)
+ * when running on Windows. No-op on other platforms.
+ */
+export function translateWslMountPath(posixPath: string): string {
+  if (process.platform !== 'win32') {
+    return posixPath;
+  }
+  const match = /^\/mnt\/([a-zA-Z])(\/.*)?$/.exec(posixPath);
+  if (match) {
+    const drive = match[1].toUpperCase();
+    const rest = match[2] ?? '';
+    return `${drive}:${rest}`;
+  }
+  return posixPath;
+}
+
 // =============================================================================
 // Validation
 // =============================================================================