feat: unified, editable frontmatter editor in publish modal

- Preset fields (from settings) are now seeded as editable/deletable rows in
  the modal alongside custom ones, using one consistent row style.
- The note's own merged frontmatter is shown as read-only (disabled) rows at
  the top of the list (only when 'Merge document frontmatter' is on, and only
  for keys not overridden by an editable row).
- Drops the separate read-only 'resolved' text preview; the rows are the
  WYSIWYG result.

Adds pure, unit-tested composeFrontmatter()/docFrontmatterToPairs() and removes
the superseded resolveFrontmatter(). Editable rows are authoritative: on a key
collision they override the merged document field. Presets are deep-copied so
editing rows never mutates saved settings.

Co-Authored-By: Claude

src/frontmatter.ts

@@ -14,12 +14,26 @@ export function parseNote(text: string): { frontmatter: Record<string, unknown>;
   return { frontmatter, body: stripped.slice(m[0].length) };
 }
 
-export function resolveFrontmatter(
-  presets: Pair[],
-  docFrontmatter: Record<string, unknown>,
-  custom: Pair[],
-  mergeDoc: boolean
-): Pair[] {
+/**
+ * Convert a parsed note's frontmatter object into ordered, stringified pairs
+ * suitable for display (read-only) and composition.
+ */
+export function docFrontmatterToPairs(docFrontmatter: Record<string, unknown>): Pair[] {
+  return Object.entries(docFrontmatter).map(([key, v]) => ({ key, value: stringifyScalar(v) }));
+}
+
+/**
+ * Build the final frontmatter for the post.
+ *
+ * Editable rows (the preset fields seeded from settings plus any custom rows
+ * the user added) are authoritative: on a key collision they win over the
+ * document's own merged fields, which appear first (and are shown read-only in
+ * the modal). Blank-key rows are dropped; duplicate editable keys keep the last
+ * value at the first position.
+ */
+export function composeFrontmatter(docPairs: Pair[], editableRows: Pair[], mergeDoc: boolean): Pair[] {
+  const editable = editableRows.filter((r) => r.key.trim() !== "");
+  const editableKeys = new Set(editable.map((r) => r.key));
   const out: Pair[] = [];
   const idx = new Map<string, number>();
   const put = (key: string, value: string) => {
@@ -27,9 +41,8 @@ export function resolveFrontmatter(
     if (at !== undefined) out[at] = { key, value };
     else { idx.set(key, out.length); out.push({ key, value }); }
   };
-  for (const p of presets) put(p.key, p.value);
-  if (mergeDoc) for (const [k, v] of Object.entries(docFrontmatter)) put(k, stringifyScalar(v));
-  for (const c of custom) put(c.key, c.value);
+  if (mergeDoc) for (const p of docPairs) if (!editableKeys.has(p.key)) put(p.key, p.value);
+  for (const r of editable) put(r.key, r.value);
   return out;
 }