fix(agents): Composer input-method Enter, autocorrect and task header layout

- Enter that commits an input-method candidate no longer sends the message.
- The composer turns off autocorrect, autocapitalisation and spellcheck, which
  popped up correction bubbles over prompts.
- The provider icon in the task header sits inline with the details instead of
  on its own line above them.

src/features/agents/Session.module.css

@@ -38,14 +38,18 @@
 .headerDetail {
   flex: 1 1 0;
   min-width: 0;
+  display: flex;
+  align-items: center;
+  gap: 4px;
   color: var(--fg-subtle);
+}
+.headerText {
+  min-width: 0;
   white-space: nowrap;
   overflow: hidden;
   text-overflow: ellipsis;
 }
 .providerIcon {
-  vertical-align: -2px;
-  margin-right: 4px;
   color: var(--fg-muted);
 }
 .muted {