feat(ui): unify overlay animations and trim tooltip delays

Use base-ui's transition-status pattern (data-starting-style /
data-ending-style) for Dialog, DropdownMenu, Select, Tooltip and Popover
so open/close animate consistently at 150ms ease-out without flicker.
Wrap dialog popups in a centered flex container so the scale animation
no longer fights with translate-based positioning, and switch
PendingChangesBar to a real Popover so it actually animates closed.

Convert ScheduledTaskEditorDialog from raw Radix to the shared Dialog
wrapper, give ScheduledTasksDialog a stable min-height to prevent layout
shift mid-animation, and reset NewWorktreeDialog form state on open
instead of close so fields don't empty during the close transition.

Drop tooltip delay from 700ms to 300ms globally and remove all
per-component overrides except the model/variant/agent selectors in the
chat input (600ms).

packages/ui/src/components/session/BranchPickerDialog.tsx

@@ -435,7 +435,7 @@ export function BranchPickerDialog({ open, onOpenChange, project }: BranchPicker
 
                     {!isEditing && !isConfirming ? (
                       <div className="flex items-center gap-1 flex-shrink-0">
-                        <Tooltip delayDuration={700}>
+                        <Tooltip>
                           <TooltipTrigger asChild>
                             <button
                               type="button"
@@ -456,7 +456,7 @@ export function BranchPickerDialog({ open, onOpenChange, project }: BranchPicker
                           </TooltipContent>
                         </Tooltip>
 
-                        <Tooltip delayDuration={700}>
+                        <Tooltip>
                           <TooltipTrigger asChild>
                             <button
                               type="button"
@@ -473,7 +473,7 @@ export function BranchPickerDialog({ open, onOpenChange, project }: BranchPicker
                           </TooltipContent>
                         </Tooltip>
 
-                        <Tooltip delayDuration={700}>
+                        <Tooltip>
                           <TooltipTrigger asChild>
                             <button
                               type="button"