feat: opt-in chat bubble layout (closes #336) (#403)

* feat(ui): opt-in chat bubble layout

Closes #336.

Adds a settings toggle that right-aligns user messages and left-aligns
assistant replies. Off by default - the current full-width layout is
friendlier to code blocks and tool output, so bubbles are strictly
opt-in per the maintainer note on the issue.

Wiring follows the existing token-usage / cli-sessions pattern:

- api/config.py: new bubble_layout bool in _SETTINGS_DEFAULTS and
  _SETTINGS_BOOL_KEYS, validated + persisted like the rest.
- static/style.css: .bubble-layout gated selectors using :has() to
  tag msg-rows by .msg-role.user / .msg-role.assistant without any JS
  changes to message creation. User rows get align-self: flex-end,
  max-width: 75%, and a row-reverse header; assistant rows flex-start.
  A 700px media query widens the max to 92% on narrow screens.
- static/index.html: new checkbox with i18n keys next to the existing
  token-usage toggle.
- static/panels.js: loads the setting into the checkbox, saves it
  back, and toggles body.bubble-layout immediately on save.
- static/boot.js: applies the class on initial load so refreshed
  tabs honor the persisted setting without a flash.
- static/i18n.js: English label + description.

Test suite errors are environmental (test server fails to start on
port 8788 on main as well).

* i18n(es): add Spanish translations for bubble_layout setting

* fix+test: boot.js bubble-layout reset on failure; add 22 tests for issue #336

* docs: v0.50.24 release — version badge and CHANGELOG

---------

Co-authored-by: Matt Van Horn <455140+mvanhorn@users.noreply.github.com>
Co-authored-by: Nathan Esquenazi <nesquena@gmail.com>

static/i18n.js

@@ -131,6 +131,7 @@ const LOCALES = {
     settings_label_theme: 'Theme',
     settings_label_language: 'Language',
     settings_label_token_usage: 'Show token usage',
+    settings_label_bubble_layout: 'Chat bubble layout',
     settings_label_cli_sessions: 'Show agent sessions',
     settings_label_sync_insights: 'Sync to insights',
     settings_label_check_updates: 'Check for updates',
@@ -183,6 +184,7 @@ const LOCALES = {
     settings_label_notifications: 'Browser notifications',
     settings_desc_notifications: 'Show a system notification when a response completes while the tab is in the background.',
     settings_desc_token_usage: 'Displays input/output token count below each assistant reply. Also toggled with /usage.',
+    settings_desc_bubble_layout: 'Right-align user messages and left-align assistant replies. Off by default to keep code blocks and tool output full-width.',
     settings_desc_cli_sessions: 'Merges sessions from the Hermes CLI (state.db) into the session list. Click a CLI session to import it and continue the conversation.',
     settings_desc_sync_insights: 'Mirrors WebUI token usage to state.db so hermes /insights includes browser session data. Off by default.',
     settings_desc_check_updates: 'Show a banner when newer versions of the WebUI or Agent are available. Runs a background git fetch periodically.',
@@ -396,6 +398,7 @@ const LOCALES = {
     settings_label_theme: 'Tema',
     settings_label_language: 'Idioma',
     settings_label_token_usage: 'Mostrar uso de tokens',
+    settings_label_bubble_layout: 'Disposición en burbujas',
     settings_label_cli_sessions: 'Mostrar sesiones de CLI',
     settings_label_sync_insights: 'Sincronizar con insights',
     settings_label_check_updates: 'Buscar actualizaciones',
@@ -448,6 +451,7 @@ const LOCALES = {
     settings_label_notifications: 'Notificaciones del navegador',
     settings_desc_notifications: 'Muestra una notificación del sistema cuando una respuesta termina mientras la pestaña está en segundo plano.',
     settings_desc_token_usage: 'Muestra el conteo de tokens de entrada/salida debajo de cada respuesta del asistente. También se puede alternar con /usage.',
+    settings_desc_bubble_layout: 'Alinea los mensajes del usuario a la derecha y las respuestas del asistente a la izquierda. Desactivado por defecto para mantener los bloques de código y la salida de herramientas a ancho completo.',
     settings_desc_cli_sessions: 'Fusiona las sesiones del CLI de Hermes (state.db) en la lista de sesiones. Haz clic en una sesión de CLI para importarla y continuar la conversación.',
     settings_desc_sync_insights: 'Refleja el uso de tokens de la WebUI en state.db para que hermes /insights incluya datos de sesiones del navegador. Desactivado por defecto.',
     settings_desc_check_updates: 'Muestra un banner cuando haya versiones más nuevas de la WebUI o del Agent. Ejecuta periódicamente un git fetch en segundo plano.',