Add timeline multi-select, reorder, and sidebar slide inspector

specs/timeline-reorder-selection.md

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+# Timeline reorder & multi-select
+
+## Goals
+
+- Right-click a slide block → **Send to Beginning** / **Send to End**
+- Multi-select slides (⌘/ctrl+click toggle, shift+click range)
+- Drag reorder moves the whole selection, preserving relative order
+- Click empty timeline clears selection
+
+## Pure module (`timeline-core/timeline.ts`)
+
+| Function | Behavior |
+| -------- | -------- |
+| `moveSlidesToBeginning(slides, indices)` | Selected slides (original order) prepended |
+| `moveSlidesToEnd(slides, indices)` | Selected slides (original order) appended |
+| `moveSlideBlock(slides, fromIndices, toIndex)` | Multi-item drag; single index delegates to `moveSlide` |
+
+## Editor shell
+
+- `selectedSlideIds: ReadonlySet<string>` in `App` (+ anchor for shift-range)
+- Settings dialog opens only when exactly one slide is selected
+- `TimelineMediaBlock`: context menu, selection ring, multi-drag via shared drag ref
+- Hint text in timeline header for selection shortcuts
+
+## Editor shell (updated)
+
+- Selection no longer opens a blocking modal
+- Per-slide overrides live in sidebar **Selected slide** accordion (auto-expands on select)
+- Multi-select shows a summary in the same accordion section
+- Sidebar accordion state is controlled in App; only auto-expands Selected slide on first select
+- Context menu exclude applies to the full selection via `toggleExcludedForIndices`
+- `moveSlideBlock` insert position mirrors `moveSlide` forward/backward semantics
+
+## Keyboard (stretch — not in initial slice)
+
+- ⌘↑ / ⌘↓ move selection block — defer unless trivial

src/components/ui/context-menu.tsx

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+import * as React from "react"
+import { ContextMenu as ContextMenuPrimitive } from "radix-ui"
+
+import { cn } from "@/lib/utils"
+import { ChevronRightIcon, CheckIcon } from "lucide-react"
+
+function ContextMenu({
+  ...props
+}: React.ComponentProps<typeof ContextMenuPrimitive.Root>) {
+  return <ContextMenuPrimitive.Root data-slot="context-menu" {...props} />
+}
+
+function ContextMenuTrigger({
+  className,
+  ...props
+}: React.ComponentProps<typeof ContextMenuPrimitive.Trigger>) {
+  return (
+    <ContextMenuPrimitive.Trigger
+      data-slot="context-menu-trigger"
+      className={cn("select-none", className)}
+      {...props}
+    />
+  )
+}
+
+function ContextMenuGroup({
+  ...props
+}: React.ComponentProps<typeof ContextMenuPrimitive.Group>) {
+  return (
+    <ContextMenuPrimitive.Group data-slot="context-menu-group" {...props} />
+  )
+}
+
+function ContextMenuPortal({
+  ...props
+}: React.ComponentProps<typeof ContextMenuPrimitive.Portal>) {
+  return (
+    <ContextMenuPrimitive.Portal data-slot="context-menu-portal" {...props} />
+  )
+}
+
+function ContextMenuSub({
+  ...props
+}: React.ComponentProps<typeof ContextMenuPrimitive.Sub>) {
+  return <ContextMenuPrimitive.Sub data-slot="context-menu-sub" {...props} />
+}
+
+function ContextMenuRadioGroup({
+  ...props
+}: React.ComponentProps<typeof ContextMenuPrimitive.RadioGroup>) {
+  return (
+    <ContextMenuPrimitive.RadioGroup
+      data-slot="context-menu-radio-group"
+      {...props}
+    />
+  )
+}
+
+function ContextMenuContent({
+  className,
+  ...props
+}: React.ComponentProps<typeof ContextMenuPrimitive.Content> & {
+  side?: "top" | "right" | "bottom" | "left"
+}) {
+  return (
+    <ContextMenuPrimitive.Portal>
+      <ContextMenuPrimitive.Content
+        data-slot="context-menu-content"
+        className={cn("z-50 max-h-(--radix-context-menu-content-available-height) min-w-36 origin-(--radix-context-menu-content-transform-origin) overflow-x-hidden overflow-y-auto rounded-lg bg-popover p-1 text-popover-foreground shadow-md ring-1 ring-foreground/10 duration-100 data-[side=bottom]:slide-in-from-top-2 data-[side=left]:slide-in-from-right-2 data-[side=right]:slide-in-from-left-2 data-[side=top]:slide-in-from-bottom-2 data-open:animate-in data-open:fade-in-0 data-open:zoom-in-95 data-closed:animate-out data-closed:fade-out-0 data-closed:zoom-out-95", className )}
+        {...props}
+      />
+    </ContextMenuPrimitive.Portal>
+  )
+}
+
+function ContextMenuItem({
+  className,
+  inset,
+  variant = "default",
+  ...props
+}: React.ComponentProps<typeof ContextMenuPrimitive.Item> & {
+  inset?: boolean
+  variant?: "default" | "destructive"
+}) {
+  return (
+    <ContextMenuPrimitive.Item
+      data-slot="context-menu-item"
+      data-inset={inset}
+      data-variant={variant}
+      className={cn(
+        "group/context-menu-item relative flex cursor-default items-center gap-1.5 rounded-md px-1.5 py-1 text-sm outline-hidden select-none focus:bg-accent focus:text-accent-foreground data-inset:pl-7 data-[variant=destructive]:text-destructive data-[variant=destructive]:focus:bg-destructive/10 data-[variant=destructive]:focus:text-destructive dark:data-[variant=destructive]:focus:bg-destructive/20 data-disabled:pointer-events-none data-disabled:opacity-50 [&_svg]:pointer-events-none [&_svg]:shrink-0 [&_svg:not([class*='size-'])]:size-4 focus:*:[svg]:text-accent-foreground data-[variant=destructive]:*:[svg]:text-destructive",
+        className
+      )}
+      {...props}
+    />
+  )
+}
+
+function ContextMenuSubTrigger({
+  className,
+  inset,
+  children,
+  ...props
+}: React.ComponentProps<typeof ContextMenuPrimitive.SubTrigger> & {
+  inset?: boolean
+}) {
+  return (
+    <ContextMenuPrimitive.SubTrigger
+      data-slot="context-menu-sub-trigger"
+      data-inset={inset}
+      className={cn(
+        "flex cursor-default items-center gap-1.5 rounded-md px-1.5 py-1 text-sm outline-hidden select-none focus:bg-accent focus:text-accent-foreground data-inset:pl-7 data-open:bg-accent data-open:text-accent-foreground [&_svg]:pointer-events-none [&_svg]:shrink-0 [&_svg:not([class*='size-'])]:size-4",
+        className
+      )}
+      {...props}
+    >
+      {children}
+      <ChevronRightIcon className="ml-auto" />
+    </ContextMenuPrimitive.SubTrigger>
+  )
+}
+
+function ContextMenuSubContent({
+  className,
+  ...props
+}: React.ComponentProps<typeof ContextMenuPrimitive.SubContent>) {
+  return (
+    <ContextMenuPrimitive.SubContent
+      data-slot="context-menu-sub-content"
+      className={cn("z-50 min-w-32 origin-(--radix-context-menu-content-transform-origin) overflow-hidden rounded-lg border bg-popover p-1 text-popover-foreground shadow-lg duration-100 data-[side=bottom]:slide-in-from-top-2 data-[side=left]:slide-in-from-right-2 data-[side=right]:slide-in-from-left-2 data-[side=top]:slide-in-from-bottom-2 data-open:animate-in data-open:fade-in-0 data-open:zoom-in-95 data-closed:animate-out data-closed:fade-out-0 data-closed:zoom-out-95", className )}
+      {...props}
+    />
+  )
+}
+
+function ContextMenuCheckboxItem({
+  className,
+  children,
+  checked,
+  inset,
+  ...props
+}: React.ComponentProps<typeof ContextMenuPrimitive.CheckboxItem> & {
+  inset?: boolean
+}) {
+  return (
+    <ContextMenuPrimitive.CheckboxItem
+      data-slot="context-menu-checkbox-item"
+      data-inset={inset}
+      className={cn(
+        "relative flex cursor-default items-center gap-1.5 rounded-md py-1 pr-8 pl-1.5 text-sm outline-hidden select-none focus:bg-accent focus:text-accent-foreground data-inset:pl-7 data-disabled:pointer-events-none data-disabled:opacity-50 [&_svg]:pointer-events-none [&_svg]:shrink-0 [&_svg:not([class*='size-'])]:size-4",
+        className
+      )}
+      checked={checked}
+      {...props}
+    >
+      <span className="pointer-events-none absolute right-2">
+        <ContextMenuPrimitive.ItemIndicator>
+          <CheckIcon
+          />
+        </ContextMenuPrimitive.ItemIndicator>
+      </span>
+      {children}
+    </ContextMenuPrimitive.CheckboxItem>
+  )
+}
+
+function ContextMenuRadioItem({
+  className,
+  children,
+  inset,
+  ...props
+}: React.ComponentProps<typeof ContextMenuPrimitive.RadioItem> & {
+  inset?: boolean
+}) {
+  return (
+    <ContextMenuPrimitive.RadioItem
+      data-slot="context-menu-radio-item"
+      data-inset={inset}
+      className={cn(
+        "relative flex cursor-default items-center gap-1.5 rounded-md py-1 pr-8 pl-1.5 text-sm outline-hidden select-none focus:bg-accent focus:text-accent-foreground data-inset:pl-7 data-disabled:pointer-events-none data-disabled:opacity-50 [&_svg]:pointer-events-none [&_svg]:shrink-0 [&_svg:not([class*='size-'])]:size-4",
+        className
+      )}
+      {...props}
+    >
+      <span className="pointer-events-none absolute right-2">
+        <ContextMenuPrimitive.ItemIndicator>
+          <CheckIcon
+          />
+        </ContextMenuPrimitive.ItemIndicator>
+      </span>
+      {children}
+    </ContextMenuPrimitive.RadioItem>
+  )
+}
+
+function ContextMenuLabel({
+  className,
+  inset,
+  ...props
+}: React.ComponentProps<typeof ContextMenuPrimitive.Label> & {
+  inset?: boolean
+}) {
+  return (
+    <ContextMenuPrimitive.Label
+      data-slot="context-menu-label"
+      data-inset={inset}
+      className={cn(
+        "px-1.5 py-1 text-xs font-medium text-muted-foreground data-inset:pl-7",
+        className
+      )}
+      {...props}
+    />
+  )
+}
+
+function ContextMenuSeparator({
+  className,
+  ...props
+}: React.ComponentProps<typeof ContextMenuPrimitive.Separator>) {
+  return (
+    <ContextMenuPrimitive.Separator
+      data-slot="context-menu-separator"
+      className={cn("-mx-1 my-1 h-px bg-border", className)}
+      {...props}
+    />
+  )
+}
+
+function ContextMenuShortcut({
+  className,
+  ...props
+}: React.ComponentProps<"span">) {
+  return (
+    <span
+      data-slot="context-menu-shortcut"
+      className={cn(
+        "ml-auto text-xs tracking-widest text-muted-foreground group-focus/context-menu-item:text-accent-foreground",
+        className
+      )}
+      {...props}
+    />
+  )
+}
+
+export {
+  ContextMenu,
+  ContextMenuTrigger,
+  ContextMenuContent,
+  ContextMenuItem,
+  ContextMenuCheckboxItem,
+  ContextMenuRadioItem,
+  ContextMenuLabel,
+  ContextMenuSeparator,
+  ContextMenuShortcut,
+  ContextMenuGroup,
+  ContextMenuPortal,
+  ContextMenuSub,
+  ContextMenuSubContent,
+  ContextMenuSubTrigger,
+  ContextMenuRadioGroup,
+}