fix(vscode): normalize Windows directory paths for SSE event store lookup (#818)

On Windows, SSE events from OpenCode arrive with native backslash
separators and system-cased drive letters (e.g. D:\Dev\...), while the
UI child store keys use forward slashes with lowercase drive letters
from VS Code's workspace folder (e.g. d:/Dev/...). This mismatch
caused the child store Map lookup to silently miss on every directory
event, preventing session data, messages, and streaming responses from
reaching the React UI.

Changes:
- sync-context.tsx: Normalize incoming SSE event directory paths by
  converting backslashes to forward slashes and uppercasing Windows
  drive letters before the child store lookup.
- useDirectoryStore.ts: Add drive letter uppercasing to
  normalizeDirectoryPath, aligning it with normalizeCandidatePath in
  client.ts and normalizeWorkspacePath in main.tsx.

Both normalizations are no-ops on macOS/Linux where paths already use
forward slashes and have no drive letters.

Closes #816

packages/ui/src/stores/useDirectoryStore.ts

@@ -45,7 +45,9 @@ const normalizeDirectoryPath = (value: string): string => {
   if (!trimmed) {
     return trimmed;
   }
-  const normalized = trimmed.replace(/\\/g, '/');
+  const normalized = trimmed
+    .replace(/\\/g, '/')
+    .replace(/^([a-z]):/, (_, letter: string) => letter.toUpperCase() + ':');
   if (normalized.length > 1) {
     return normalized.replace(/\/+$/, '');
   }

packages/ui/src/sync/sync-context.tsx

@@ -108,10 +108,16 @@ function isRecentBoot() {
 }
 
 function handleEvent(
-  directory: string,
+  rawDirectory: string,
   payload: Event,
   childStores: ChildStoreManager,
 ) {
+  // Normalize directory path: SSE events from OpenCode use native OS separators
+  // (backslashes on Windows) and may differ in drive-letter case.
+  // Child stores are keyed with forward slashes and uppercase drive letters.
+  const directory = rawDirectory && rawDirectory !== "global"
+    ? rawDirectory.replace(/\\/g, "/").replace(/^([a-z]):/, (_, l: string) => l.toUpperCase() + ":")
+    : rawDirectory
   // Global events
   if (directory === "global" || !directory) {
     const recent = isRecentBoot()