Fix re-saving drafts with existing media

When re-saving a draft, the code was trying to copy media files that
were already in drafts storage to new locations, causing copy errors.

Changes:
- Add extractLocalIdFromPath() to detect if a path is already in drafts
- Track loadedMediaMap in ComposerState for identifying reusable media
- Only delete old media that wasn't reused during re-save
- Pass loadedMediaMap when saving to enable media reuse detection
- Disable pointer events on draft media preview

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

src/view/com/composer/Composer.tsx

@@ -353,6 +353,7 @@ export const ComposePost = ({
         composerState,
         replyTo,
         existingDraftId: composerState.draftId,
+        loadedMediaMap: composerState.loadedMediaMap,
       })
       composerDispatch({type: 'mark_saved', draftId: savedDraft.id})
       onClose()
@@ -368,6 +369,7 @@ export const ComposePost = ({
       composerState,
       replyTo,
       existingDraftId: composerState.draftId,
+      loadedMediaMap: composerState.loadedMediaMap,
     })
     composerDispatch({type: 'mark_saved', draftId: savedDraft.id})
   }, [saveDraft, composerState, replyTo, composerDispatch])

src/view/com/composer/drafts/DraftItem.tsx

@@ -266,7 +266,7 @@ function DraftMediaPreview({post}: {post: DraftPostDisplay}) {
   }
 
   return (
-    <View style={[a.pt_xs]}>
+    <View style={[a.pt_xs, a.pointer_events_none]}>
       {/* Images - use real embed components */}
       {viewImages.length === 1 && (
         <AutoSizedImage image={viewImages[0]} hideBadge />

src/view/com/composer/state/composer.ts

@@ -106,6 +106,8 @@ export type ComposerState = {
   draftId?: string
   /** Whether the composer has been modified since loading a draft. */
   isDirty: boolean
+  /** Map of localId -> loaded media path/URL for the current draft. Used for re-saving without re-copying media. */
+  loadedMediaMap?: Map<string, string>
 }
 
 export type ComposerAction =
@@ -317,6 +319,7 @@ export function composerReducer(
         mutableNeedsFocusActive: true,
         draftId: draft.id,
         isDirty: false,
+        loadedMediaMap: loadedMedia,
         thread: {
           posts,
           postgate: draft.postgate || state.thread.postgate,
@@ -330,6 +333,7 @@ export function composerReducer(
         mutableNeedsFocusActive: true,
         draftId: undefined,
         isDirty: false,
+        loadedMediaMap: undefined,
         thread: {
           posts: [
             {