fix: move heading-into-heading bumps levels through the whole block

moveBlock now accepts headingBump. trySurgicalEdit for moveNodeIn/
Before/After detects when both source and target are headings and
computes the bump so the moved block lands at the correct level:
- moveNodeIn into H2 makes the source heading H3 and every nested
  heading shifts +1 too (capped at H6)
- moveNodeBefore/After against a heading keeps the source at the
  target's level and bumps nested headings by the same delta.

For list-item targets the previous list-marker conversion is
preserved, so we don't break those cases.

Also add a transient toast (store.errorMessage) so when a structural
mindmap op has no surgical handler the user sees that markdown wasn't
updated.

Co-Authored-By: Claude <noreply@anthropic.com>
Signed-off-by: Andrei Kvapil <kvapss@gmail.com>

Author: kvaps

src/App.vue

@@ -80,6 +80,10 @@ function onDragEnd(e: PointerEvent) {
 
 <template>
   <div ref="appRef" :class="rootClass">
+    <div v-if="store.errorMessage" class="app__toast" @click="store.setError(null)">
+      <span>{{ store.errorMessage }}</span>
+      <button type="button" class="app__toast-close" aria-label="Dismiss">×</button>
+    </div>
     <div class="app__editor" :style="editorStyle"><Editor /></div>
     <div
       v-if="!dividerHidden"
@@ -151,6 +155,33 @@ html, body, #app {
   height: 100%;
   overflow: hidden;
 }
+.app__toast {
+  position: fixed;
+  bottom: 20px;
+  left: 50%;
+  transform: translateX(-50%);
+  background: #c62828;
+  color: #fff;
+  padding: 10px 16px 10px 18px;
+  border-radius: 6px;
+  font-size: 13px;
+  box-shadow: 0 4px 16px rgba(0, 0, 0, 0.25);
+  display: flex;
+  align-items: center;
+  gap: 12px;
+  z-index: 1000;
+  cursor: pointer;
+  max-width: 80vw;
+}
+.app__toast-close {
+  background: transparent;
+  border: none;
+  color: #fff;
+  font-size: 18px;
+  line-height: 1;
+  cursor: pointer;
+  padding: 0 2px;
+}
 .app__divider {
   flex: 0 0 6px;
   background: var(--divider-bg);

src/components/MindMap.vue

@@ -315,20 +315,33 @@ function trySurgicalEdit(op: unknown): boolean {
       let newIndent: number
       let newMarker: string | null = null
       let targetLine: number
+      let headingBump = 0
       if (o.name === 'moveNodeIn') {
         newIndent = (toMeta.indent ?? 0) + (toMeta.kind === 'listItem' ? 2 : 0)
         targetLine = blockEnd(to) + 1
-        newMarker = '- '
+        if (meta.kind === 'heading' && toMeta.kind === 'heading') {
+          headingBump = (toMeta.level ?? 1) + 1 - (meta.level ?? 1)
+        } else {
+          newMarker = '- '
+        }
       } else if (o.name === 'moveNodeBefore') {
         newIndent = toMeta.indent ?? 0
         targetLine = toMeta.startLine
-        newMarker = toMeta.kind === 'heading' ? (toMeta.marker ?? null) : '- '
+        if (meta.kind === 'heading' && toMeta.kind === 'heading') {
+          headingBump = (toMeta.level ?? 1) - (meta.level ?? 1)
+        } else {
+          newMarker = toMeta.kind === 'heading' ? (toMeta.marker ?? null) : '- '
+        }
       } else {
         newIndent = toMeta.indent ?? 0
         targetLine = blockEnd(to) + 1
-        newMarker = toMeta.kind === 'heading' ? (toMeta.marker ?? null) : '- '
+        if (meta.kind === 'heading' && toMeta.kind === 'heading') {
+          headingBump = (toMeta.level ?? 1) - (meta.level ?? 1)
+        } else {
+          newMarker = toMeta.kind === 'heading' ? (toMeta.marker ?? null) : '- '
+        }
       }
-      md = moveBlock(md, effMeta, newIndent, newMarker, targetLine)
+      md = moveBlock(md, effMeta, newIndent, newMarker, targetLine, headingBump)
     }
     return commitMarkdown(md)
   }
@@ -835,7 +848,25 @@ onMounted(() => {
       if (el) el.style.visibility = 'hidden'
       return
     }
-    if (trySurgicalEdit(op)) return
+    const handled = trySurgicalEdit(op)
+    if (handled) return
+    const mutationOps = new Set([
+      'addChild',
+      'insertSibling',
+      'insertParent',
+      'removeNodes',
+      'moveUpNode',
+      'moveDownNode',
+      'moveNodeIn',
+      'moveNodeBefore',
+      'moveNodeAfter',
+      'copyNode',
+      'copyNodes',
+      'reshapeNode',
+    ])
+    if (op?.name && mutationOps.has(op.name as string)) {
+      store.setError(`Markdown not updated for "${op.name}" — mindmap may be out of sync`)
+    }
     // No surgical handler — skip markdown update rather than reformatting everything.
     // Next surgical op will re-sync from the (possibly stale) markdown side.
   })

src/stores/document.ts

@@ -104,6 +104,8 @@ export const useDocumentStore = defineStore('document', () => {
   const cursorSource = ref<'editor' | 'mindmap' | null>(null)
   const undoHandler = ref<(() => boolean) | null>(null)
   const redoHandler = ref<(() => boolean) | null>(null)
+  const errorMessage = ref<string | null>(null)
+  let errorTimer: number | null = null
 
   watch(
     [markdown, viewMode, splitRatio, theme],
@@ -149,13 +151,25 @@ export const useDocumentStore = defineStore('document', () => {
     return redoHandler.value?.() ?? false
   }
 
+  function setError(msg: string | null, autoDismissMs = 5000) {
+    errorMessage.value = msg
+    if (errorTimer) window.clearTimeout(errorTimer)
+    if (msg && autoDismissMs > 0) {
+      errorTimer = window.setTimeout(() => {
+        errorMessage.value = null
+        errorTimer = null
+      }, autoDismissMs)
+    }
+  }
+
   return {
     markdown,
     viewMode,
     splitRatio,
     theme,
     cursorLine,
     cursorSource,
+    errorMessage,
     setMarkdown,
     setViewMode,
     setSplitRatio,
@@ -164,5 +178,6 @@ export const useDocumentStore = defineStore('document', () => {
     registerHistory,
     undo,
     redo,
+    setError,
   }
 })

src/utils/surgical.ts

@@ -178,13 +178,22 @@ export function moveBlock(
   fromMeta: NodeMeta,
   newIndent: number,
   newMarker: string | null,
-  insertBeforeLine: number
+  insertBeforeLine: number,
+  headingBump = 0
 ): string {
   const lines = markdown.split('\n')
   const blockLen = fromMeta.endLine - fromMeta.startLine + 1
   const block = lines.slice(fromMeta.startLine, fromMeta.endLine + 1)
   const indentDelta = newIndent - (fromMeta.indent ?? 0)
   const adjusted = block.map((line, i) => {
+    if (headingBump !== 0) {
+      const h = line.match(/^(\s*)(#{1,6})\s/)
+      if (h) {
+        const oldLen = h[2].length
+        const newLen = Math.max(1, Math.min(6, oldLen + headingBump))
+        return h[1] + '#'.repeat(newLen) + line.slice(h[1].length + oldLen)
+      }
+    }
     if (i === 0 && newMarker) {
       const m = line.match(/^(\s*)(?:[-*+]|\d+[.)])\s+(.*)$/)
       if (m) return ' '.repeat(newIndent) + newMarker + m[2]