fix(rich-markdown-editor): tighten read-only gate for uppercase entities and orphan ref-defs

Two silent-corruption cases the idempotency probe can't see:

- The HTML-entity safe-list used a case-insensitive regex, so `&`/`<`/`>` were
  treated as the round-trippable canonical entities and let through as editable, but the
  serializer only round-trips the lowercase forms and mangles the uppercase ones. Make the
  safe-list case-sensitive.
- An unused reference definition (`[x]: url` with no `[x]` reference) is dropped entirely on
  serialize, a deletion the idempotency probe misses. Detect orphan definitions and open
  read-only; used definitions still inline losslessly and stay editable.

Author: waleedlatif1

apps/sim/app/workspace/[workspaceId]/files/components/file-viewer/rich-markdown-editor/round-trip-safety.test.ts

@@ -55,6 +55,16 @@ describe('isRoundTripSafe', () => {
     expect(isRoundTripSafe('a b')).toBe(false)
     expect(isRoundTripSafe('a & b < c > d')).toBe(true)
     expect(isRoundTripSafe('AT&T and R&D')).toBe(true)
+    expect(isRoundTripSafe('a & b')).toBe(false)
+    expect(isRoundTripSafe('a < b > c')).toBe(false)
+  })
+
+  it('rejects an orphan reference definition (serializer drops it) but allows used ones', () => {
+    expect(isRoundTripSafe('Some text.\n\n[unused]: https://example.com "title"')).toBe(false)
+    expect(isRoundTripSafe('[a]: u1\n[b]: u2\n\nuse only [a]')).toBe(false)
+    expect(isRoundTripSafe('See [x][1].\n\n[1]: https://example.com "T"')).toBe(true)
+    expect(isRoundTripSafe('A [shortcut] ref.\n\n[shortcut]: https://example.com')).toBe(true)
+    expect(isRoundTripSafe('Case [Foo] insensitive.\n\n[foo]: https://example.com')).toBe(true)
   })
 
   it('does not flag HTML/comments/entities inside tilde or nested code fences', () => {

apps/sim/app/workspace/[workspaceId]/files/components/file-viewer/rich-markdown-editor/round-trip-safety.ts

@@ -24,14 +24,16 @@ const PROBE_SIZE_LIMIT = 256 * 1024
  *   flattens `one<br>two` to `one two`. Matched on a table-shaped line (≥2 pipes) containing a `<br>`.
  * - **Hard break inside a heading** (trailing two spaces or a backslash) — the serializer splits
  *   the heading, ejecting the second line into a separate paragraph.
- * - **HTML entity** other than `&amp;`/`&lt;`/`&gt;` (e.g. `&copy;`, `&#39;`, `&nbsp;`) — the
- *   serializer escapes the `&`, turning the rendered character into literal entity source. A bare
- *   `&` with no `;` is left alone (it re-renders identically, so it's harmless churn).
+ * - **HTML entity** other than the lowercase canonical `&amp;`/`&lt;`/`&gt;` (e.g. `&copy;`, `&#39;`,
+ *   `&nbsp;`, or the uppercase `&AMP;`) — the serializer escapes the `&`, turning the rendered character
+ *   into literal entity source. The safe-list is deliberately case-*sensitive*: `@tiptap/markdown` only
+ *   round-trips the lowercase forms, so `&AMP;`/`&LT;`/`&GT;` must fall through to read-only rather than
+ *   be treated as safe. A bare `&` with no matching `;`-terminated name is left alone (harmless churn).
  */
 const STABLE_LOSS_PATTERNS: ReadonlyArray<RegExp> = [
   /^(?=(?:[^\n]*\|){2})[^\n]*<br\s*\/?>/im,
   /^#{1,6}\s.*(?: {2,}|\\)$/m,
-  /&(?!(?:amp|lt|gt);)(?:#x?[0-9a-f]+|[a-z][a-z0-9]*);/i,
+  /&(?!(?:amp|lt|gt);)(?:#x?[0-9a-fA-F]+|[a-zA-Z][a-zA-Z0-9]*);/,
 ]
 
 /**
@@ -60,6 +62,35 @@ function linkedImageCount(content: string): number {
   return content.match(LINKED_IMAGE_PATTERN)?.length ?? 0
 }
 
+/** A reference definition line: `[label]: destination "optional title"` (up to 3 leading spaces). */
+const REFERENCE_DEFINITION = /^ {0,3}\[([^\]]+)]:[ \t]+\S[^\n]*$/gm
+
+/** CommonMark reference labels match case-insensitively with internal whitespace collapsed. */
+function normalizeReferenceLabel(label: string): string {
+  return label.trim().replace(/\s+/g, ' ').toLowerCase()
+}
+
+/**
+ * True when `content` defines a link/image reference that nothing uses. A *used* reference inlines
+ * losslessly on serialize (`[x][id]` + `[id]: url` → `[x](url)`), but an *unused* definition is dropped
+ * entirely — a silent deletion the idempotency probe can't see (the drop happens on the first pass,
+ * which is then stable). We open such a file read-only rather than lose the definition on first edit.
+ * Conservative: a label counts as used if it appears bracketed anywhere in the body, so the rare
+ * inline-text collision errs toward editable, never toward a false read-only.
+ */
+function hasOrphanReferenceDefinition(content: string): boolean {
+  const labels = new Set<string>()
+  for (const match of content.matchAll(REFERENCE_DEFINITION)) {
+    labels.add(normalizeReferenceLabel(match[1]))
+  }
+  if (labels.size === 0) return false
+  const body = content.replace(REFERENCE_DEFINITION, '').replace(/\s+/g, ' ').toLowerCase()
+  for (const label of labels) {
+    if (!body.includes(`[${label}]`)) return true
+  }
+  return false
+}
+
 /**
  * Whether `content` survives the editor's markdown round-trip without data loss or autosave
  * churn. The editor opens the content read-only when this is false, so the probe is deliberately
@@ -75,6 +106,7 @@ export function isRoundTripSafe(content: string): boolean {
   if (content.length > PROBE_SIZE_LIMIT) return false
   const stripped = stripCode(content)
   if (STABLE_LOSS_PATTERNS.some((pattern) => pattern.test(stripped))) return false
+  if (hasOrphanReferenceDefinition(stripped)) return false
   try {
     const once = serializeMarkdownDocument(content)
     if (linkedImageCount(stripped) !== linkedImageCount(stripCode(once))) return false