feat(ui): add composer enter-to-send toggle (#3178)

* feat(ui): add composer enter-to-send toggle and native hardware-keyboard detection

Replaces the settings-page "Enter sends with a keyboard attached" checkbox with
an EnterKeyToggle in the composer footer: plain Enter submits / Shift+Enter
inserts a newline when enabled, Shift+Enter submits / Enter inserts a newline
when disabled. Ctrl/Cmd+Enter always submits as the soft-keyboard fallback.
Persisted as enterToSend.

Adds the Android HardwareKeyboardPlugin: scans input devices for an alphabetic
physical keyboard (ignoring phantom key/sensor devices), re-answers on config
changes/foreground, and confirms attachment from real hardware key events.
MainActivity surfaces key events to it before the WebView consumes them. The
composer and draft layout start keyboard-aware instead of inferring one focus
late; ComposerEditor preserves Enter modifiers through CodeMirror's deferred
re-dispatch so the toggle can tell Shift/Ctrl+Enter from plain Enter.

Removes the settings search entry and i18n keys for the old checkbox.

* refactor(ui): keep enter-to-send branch focused

* fix(ui): preserve enter-toggle taps on touch

* fix(ui): preserve enter key defaults and move setting

* fix(ui): keep enter setting lint-clean

* fix(i18n): preserve current Turkish message parity

* fix(settings): persist enter-to-send preference

* fix(ui): clarify enter-to-send setting

* fix(ui): apply enter preference on desktop

* fix(ui): match enter setting focus mode default

* test(ui): cover enter key policy matrix

* fix(ui): harden deferred enter handling

* fix(chat): preserve untouched Enter policy and validate settings

---------

Co-authored-by: Bohdan Triapitsyn <artmore@protonmail.com>

packages/ui/src/components/chat/composer/DOCUMENTATION.md

@@ -218,3 +218,18 @@ on the strength of type-check and unit tests.
 
 Run tests per file (`bun test <path>`): `mock.module` is process-global, so
 suites that install module mocks are order-dependent.
+
+## Enter preference
+
+`keyboardPolicy.ts` owns the submission decision. Until the Chat setting is
+changed, desktop Enter sends, mobile and focus mode require Ctrl/Cmd+Enter,
+and Shift-modified Enter does not send. An explicit choice applies across
+shared composers; Ctrl/Cmd+Enter sends in either configured mode.
+
+CodeMirror's deferred mobile Enter loses modifier information. Untouched
+settings restore Shift to keep the original policy. Once configured, with mobile
+autocapitalization enabled, the editor cannot distinguish its Shift flag from
+an intentional Shift press and does not restore Shift. Consequently, deferred
+Shift+Enter can send when Enter-to-send is enabled and cannot serve as the send
+shortcut when it is disabled. Ctrl/Cmd+Enter remains the supported modified
+send shortcut on this path.