feat: compose new email with contact autocomplete and AI drafting (#616)

* feat: compose new email with contact autocomplete and AI drafting

- Add a compose-new-email box to the email view with a recipient field
  that autocompletes from Gmail contacts (keyboard navigation, match
  highlighting, avatar chips)
- Build contact indices in core: gmail_sent_contacts syncs the SENT
  label via the Gmail API for full coverage of people you've emailed,
  with gmail_contacts as an instant local-snapshot fallback; both are
  pre-warmed at startup so the first keystroke is instant
- Add generateOneShot() one-shot text generation for the composer's
  "write with AI", resolving to the active default model/provider
- Add getAccountName() (parsed from a recent SENT message's From
  header, no extra OAuth scope) so AI drafts sign off with the real name
- New IPC channels: gmail:searchContacts, gmail:getAccountName,
  llm:generate, llm:getDefaultModel

* feat: attachments, undo/redo, and unified compose for new emails

- Merge ComposeNewBox into ComposeBox via a new 'new' mode, memoizing the
  component so inbox sync ticks no longer jank the open composer.
- Add file attachments: stage files in the renderer (25MB cap), pass raw
  base64 over IPC, and build a multipart/mixed MIME on send.
- Add undo/redo buttons to the compose toolbar.
- Single Write/Edit AI bar that generates a draft, then iteratively rewrites
  it; drop the hardcoded Gemini Flash model and use the default Copilot model.
- Suppress inbox reloads while the compose-new modal is open.
- Log llm:generate provider/model/output for debugging.

* fix: remove redundant Subject placeholder in composer

The subject row already has a 'Subject' gutter label, so the input's
placeholder repeated the word — an empty field read 'Subject' twice.
Drop the placeholder to match the To/Cc/Bcc fields.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

---------

Co-authored-by: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

apps/x/packages/shared/src/ipc.ts

@@ -190,6 +190,15 @@ const ipcSchemas = {
       bodyText: z.string(),
       inReplyTo: z.string().optional(),
       references: z.string().optional(),
+      attachments: z
+        .array(
+          z.object({
+            filename: z.string(),
+            mimeType: z.string(),
+            contentBase64: z.string(),
+          }),
+        )
+        .optional(),
     }),
     res: z.object({
       messageId: z.string().optional(),
@@ -211,6 +220,12 @@ const ipcSchemas = {
       email: z.string().nullable(),
     }),
   },
+  'gmail:getAccountName': {
+    req: z.object({}),
+    res: z.object({
+      name: z.string().nullable(),
+    }),
+  },
   'gmail:archiveThread': {
     req: z.object({ threadId: z.string().min(1) }),
     res: z.object({ ok: z.boolean(), error: z.string().optional() }),
@@ -388,6 +403,27 @@ const ipcSchemas = {
       error: z.string().optional(),
     }),
   },
+  'llm:getDefaultModel': {
+    req: z.null(),
+    res: z.object({
+      model: z.string(),
+      provider: z.string(),
+    }),
+  },
+  'llm:generate': {
+    req: z.object({
+      prompt: z.string().min(1),
+      system: z.string().optional(),
+      model: z.string().optional(),
+      provider: z.string().optional(),
+    }),
+    res: z.object({
+      text: z.string().optional(),
+      model: z.string().optional(),
+      provider: z.string().optional(),
+      error: z.string().optional(),
+    }),
+  },
   'models:saveConfig': {
     req: LlmModelConfig,
     res: z.object({