fix: resolve all TS errors, ESLint warnings, and npm warnings bump to v0.3.12

- Pin all @milkdown/* packages to exact 7.21.1, add phantom-dep plugins as direct deps

- Fix TextSelection.create type error in useMilkdown.ts

- Fix Backspace auto-pair dead-code bug (unreachable due to PAIRS check order)

- Extract parseHeadings/Heading to outlineUtils.ts (react-refresh fix)

- Extract StatusBar item components to StatusBarItems.tsx (react-refresh fix)

- Configure npm allowScripts for electron and esbuild postinstall

- Update QUALITY_REVIEW_REPORT.json with all fixes applied

- Bump version to 0.3.12

src/renderer/components/OutlinePanel/outlineUtils.ts

@@ -0,0 +1,27 @@
+export interface Heading {
+  level: number
+  text: string
+  /** Position in document (character offset from markdown source) */
+  pos: number
+}
+
+const HEADING_RE = /^(#{1,6})\s+(.+)$/gm
+
+/**
+ * Parse headings from raw markdown content using regex.
+ */
+export function parseHeadings(markdown: string): Heading[] {
+  const headings: Heading[] = []
+  let match: RegExpExecArray | null
+
+  // Reset regex state
+  HEADING_RE.lastIndex = 0
+
+  while ((match = HEADING_RE.exec(markdown)) !== null) {
+    const level = match[1].length
+    const text = match[2].trim()
+    headings.push({ level, text, pos: match.index })
+  }
+
+  return headings
+}