fix(studio): enable timeline resize for all elements, improve perf and UX

Enable trim-start and trim-end for all authored timeline elements (divs,
sections, compositions) — not just video/audio/img. The deterministic-window
gate was overly restrictive since all non-implicit elements have authored
data-start/data-duration that define their timeline window.

Replace iframe reload after resize/move with direct DOM attribute patching
via patchIframeDomTiming(). This eliminates playhead-jump-to-zero, visual
blinking, and race conditions from file-watcher echoes. File persistence
runs in a serialized background queue (persistTimelineEdit + enqueueEdit)
so rapid edits don't overwrite each other.

Add mediabunny-based media probe service (mediaProbe.ts) for fast metadata
extraction from file headers. Timeline elements missing sourceDuration are
enriched asynchronously without waiting for DOM loadedmetadata events.

Tune the runtime media preloader: lower lazy threshold from 6 to 3 clips,
add 3s lookbehind window for reverse scrub, adaptive promoted-clip cap.

Deduplicate getTimelineEditCapabilities — computed once in TimelineCanvas
and passed as a prop to TimelineClip instead of recomputing per clip.

Remove dead PlaybackAdapter re-export from useTimelinePlayer — all consumers
import directly from playbackTypes.

packages/studio/src/player/components/TimelineClip.tsx

@@ -3,7 +3,7 @@ import type { TimelineTrackStyle } from "./timelineTheme";
 import { memo, type ReactNode } from "react";
 import type { TimelineElement } from "../store/playerStore";
 import { defaultTimelineTheme, getClipHandleOpacity, type TimelineTheme } from "./timelineTheme";
-import { getTimelineEditCapabilities } from "./timelineEditing";
+import type { TimelineEditCapabilities } from "./timelineEditing";
 
 interface TimelineClipProps {
   el: TimelineElement;
@@ -13,6 +13,7 @@ interface TimelineClipProps {
   isHovered: boolean;
   isDragging?: boolean;
   hasCustomContent: boolean;
+  capabilities: TimelineEditCapabilities;
   theme?: TimelineTheme;
   trackStyle: TimelineTrackStyle;
   isComposition: boolean;
@@ -33,6 +34,7 @@ export const TimelineClip = memo(function TimelineClip({
   isHovered,
   isDragging = false,
   hasCustomContent,
+  capabilities,
   theme = defaultTimelineTheme,
   trackStyle,
   isComposition,
@@ -47,6 +49,7 @@ export const TimelineClip = memo(function TimelineClip({
   const leftPx = el.start * pps;
   const widthPx = Math.max(el.duration * pps, 4);
   const handleOpacity = getClipHandleOpacity({ isHovered, isSelected, isDragging });
+
   const borderColor = isSelected
     ? theme.clipBorderActive
     : isHovered
@@ -59,7 +62,6 @@ export const TimelineClip = memo(function TimelineClip({
       : isHovered
         ? theme.clipShadowHover
         : theme.clipShadow;
-  const capabilities = getTimelineEditCapabilities(el);
   const displayLabel = el.label || el.id || el.tag;
   const showHandles = handleOpacity > 0.01;