refactor: update keyboard shortcuts to prevent conflicts (#100)

Change Keyboard Shortcuts dialog shortcut from Cmd+H to Cmd+.
Update memory debug shortcut from Cmd+Shift+M to Cmd+Shift+D
Modify model selector shortcut to use Cmd+Shift+M

packages/ui/src/components/layout/Header.tsx

@@ -425,7 +425,7 @@ export const Header: React.FC = () => {
             </button>
           </TooltipTrigger>
           <TooltipContent>
-            <p>Keyboard Shortcuts ({getModifierLabel()}+H)</p>
+            <p>Keyboard Shortcuts ({getModifierLabel()}+.)</p>
           </TooltipContent>
         </Tooltip>
       </div>

packages/ui/src/components/ui/CommandPalette.tsx

@@ -137,7 +137,7 @@ export const CommandPalette: React.FC = () => {
           <CommandItem onSelect={handleShowHelp}>
             <RiQuestionLine className="mr-2 h-4 w-4" />
             <span>Keyboard Shortcuts</span>
-            <CommandShortcut>{getModifierLabel()} + H</CommandShortcut>
+            <CommandShortcut>{getModifierLabel()} + .</CommandShortcut>
           </CommandItem>
           <CommandItem onSelect={handleOpenDiffPanel}>
             <RiCodeLine className="mr-2 h-4 w-4" />

packages/ui/src/components/ui/HelpDialog.tsx

@@ -94,7 +94,7 @@ export const HelpDialog: React.FC = () => {
           icon: RiCommandLine,
         },
         {
-          keys: [`${mod} + H`],
+          keys: [`${mod} + .`],
           description: "Show Keyboard Shortcuts (this dialog)",
           icon: RiQuestionLine,
         },
@@ -104,7 +104,7 @@ export const HelpDialog: React.FC = () => {
           icon: RiLayoutLeftLine,
         },
         {
-          keys: [`${mod} + M`],
+          keys: [`Shift + ${mod} + M`],
           description: "Open Model Selector",
           icon: RiBrainAi3Line,
         },