feat(desktop): rebindable keyboard shortcuts panel

Add a central keybind registry + nanostore so desktop hotkeys are
discoverable and user-rebindable. A titlebar ⌨ button (and ⌘/) opens a
collapsible map grouped by Composer (read-only) / Profiles / Session /
Navigation / View; click any chip to capture a new combo. Overrides
persist to localStorage as a delta against shipped defaults, so future
default changes aren't shadowed by a stored snapshot.

Migrates the previously scattered inline listeners (palette, command
center, new session, sidebar, theme) into the registry, and adds profile
switch/cycle/create + default-profile hotkeys.

apps/desktop/src/app/chat/composer/help-hint.tsx

@@ -5,7 +5,7 @@ import { useI18n } from '@/i18n'
 import { COMPLETION_DRAWER_CLASS } from './completion-drawer'
 
 const COMMON_COMMAND_KEYS = ['/help', '/clear', '/resume', '/details', '/copy', '/quit']
-const HOTKEY_KEYS = ['@', '/', '?', 'Enter', 'Cmd/Ctrl+K', 'Cmd/Ctrl+L', 'Esc', '↑ / ↓']
+const HOTKEY_KEYS = ['@', '/', '?', 'Enter', 'Cmd/Ctrl+Shift+K', 'Cmd/Ctrl+/', 'Esc', '↑ / ↓']
 
 export function HelpHint() {
   const { t } = useI18n()

apps/desktop/src/app/chat/sidebar/profile-switcher.tsx

@@ -34,6 +34,7 @@ import { cn } from '@/lib/utils'
 import {
   $activeGatewayProfile,
   $profileColors,
+  $profileCreateRequest,
   $profileOrder,
   $profiles,
   $profileScope,
@@ -178,6 +179,20 @@ export function ProfileRail() {
     void refreshActiveProfile()
   }, [])
 
+  // Open the create dialog when the `profile.create` hotkey fires (the dialog
+  // state lives here, so the global keybind bumps a request atom we watch).
+  const createRequest = useStore($profileCreateRequest)
+  const lastCreateRef = useRef(createRequest)
+
+  useEffect(() => {
+    if (createRequest === lastCreateRef.current) {
+      return
+    }
+
+    lastCreateRef.current = createRequest
+    setCreateOpen(true)
+  }, [createRequest])
+
   return (
     <div aria-label="Profiles" className="flex items-center gap-0.5" role="tablist">
       {/* One button toggles default ↔ all: home face when scoped to a profile,
@@ -199,7 +214,12 @@ export function ProfileRail() {
 
       {/* Single-profile: the active default's home icon next to the create +. */}
       {!multiProfile && defaultProfile && (
-        <ProfilePill active glyph="home" label={defaultProfile.name} onSelect={() => selectProfile(defaultProfile.name)} />
+        <ProfilePill
+          active
+          glyph="home"
+          label={defaultProfile.name}
+          onSelect={() => selectProfile(defaultProfile.name)}
+        />
       )}
 
       <div