Mark composer as clean after saving draft

Add mark_saved action that resets isDirty to false and updates the
draftId. This is dispatched after successfully saving a draft, allowing
the user to close the composer without a discard prompt since their
changes have been saved.

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

src/view/com/composer/Composer.tsx

@@ -349,26 +349,28 @@ export const ComposePost = ({
 
   const handleSaveDraft = React.useCallback(async () => {
     try {
-      await saveDraft({
+      const savedDraft = await saveDraft({
         composerState,
         replyTo,
         existingDraftId: composerState.draftId,
       })
+      composerDispatch({type: 'mark_saved', draftId: savedDraft.id})
       onClose()
     } catch (e) {
       logger.error('Failed to save draft', {error: e})
       setError(_(msg`Failed to save draft`))
     }
-  }, [saveDraft, composerState, replyTo, onClose, _])
+  }, [saveDraft, composerState, replyTo, composerDispatch, onClose, _])
 
   // Save without closing - for use by DraftsButton
   const saveCurrentDraft = React.useCallback(async () => {
-    await saveDraft({
+    const savedDraft = await saveDraft({
       composerState,
       replyTo,
       existingDraftId: composerState.draftId,
     })
-  }, [saveDraft, composerState, replyTo])
+    composerDispatch({type: 'mark_saved', draftId: savedDraft.id})
+  }, [saveDraft, composerState, replyTo, composerDispatch])
 
   // Check if composer is empty (no content to save)
   const isComposerEmpty = React.useMemo(() => {

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

@@ -136,6 +136,10 @@ export type ComposerAction =
   | {
       type: 'clear'
     }
+  | {
+      type: 'mark_saved'
+      draftId: string
+    }
 
 export const MAX_IMAGES = 4
 
@@ -346,6 +350,13 @@ export function composerReducer(
         },
       }
     }
+    case 'mark_saved': {
+      return {
+        ...state,
+        isDirty: false,
+        draftId: action.draftId,
+      }
+    }
   }
 }