#11527: feat(control-ui): UX improvements — Enter key, thinking icon, auto-chat

Three small UX enhancements for the Control UI: ### 1. Enter key on password field triggers Connect Users expect to press Enter after typing a password. The password field (not stored, entered every session) now submits on Enter. ### 2. Thinking toggle icon reflects state - **On**: Brain icon (🧠) - **Off**: Circle icon (⭕) Provides clear visual feedback beyond the CSS `active` class highlight. ### 3. Auto-switch to Chat tab after connection When connecting from the Overview page, automatically switches to the Chat tab on successful `onHello`. Saves a click since most users connect to chat. ## Changes - `ui/src/ui/views/overview.ts`: Add `@keydown` handler to password input - `ui/src/ui/app-render.helpers.ts`: Conditional icon for thinking toggle - `ui/src/ui/app-gateway.ts`: Switch to chat tab in `onHello` callback All three are independent, small changes. Happy to split into separate PRs if preferred. <!-- greptile_comment --> <h2>Greptile Overview</h2> <h3>Greptile Summary</h3> This PR adds three Control UI UX tweaks: submitting the password field with Enter on the Overview page, showing a different icon for the thinking toggle based on state, and auto-switching to the Chat tab after a successful gateway hello. The main integration concern is in the new auto-switch logic in `app-gateway.ts`: it switches tabs by calling `host.setTab("chat")` directly from the gateway connect layer, which can bypass the existing tab-change machinery in `app-settings.ts` that synchronizes URL state and runs per-tab side effects (polling/refresh). The other changes look localized and consistent with existing patterns. <h3>Confidence Score: 4/5</h3> - Mostly safe to merge, but fix the tab-switch implementation to use the standard tab-change path. - Changes are small and localized. The thinking icon and Enter-to-connect behavior look correct, but the onHello auto-switch currently calls `host.setTab` directly, which can bypass required side effects handled in `app-settings.ts:setTab`/`setTabInternal`. Fixing that should make the PR low-risk. - ui/src/ui/app-gateway.ts <!-- greptile_other_comments_section --> <!-- /greptile_comment -->