fix(git-sync): round-trip paragraph/heading text alignment (review #10)

Aligned paragraphs were exported as <div align="…"> which had NO matching
import parse rule — the div was unwrapped and the alignment lost on every
round trip. Emit a styled <p style="text-align:…"> instead, and give the
textAlign global attribute (docmost-schema) an explicit parseHTML that reads
element.style.textAlign (and legacy align=) plus a renderHTML that writes the
style. Now heading/paragraph alignment survives Docmost->git->Docmost.

Verified on stand: a textAlign=center paragraph exports as
<p style="text-align:center">, and after a git-side edit + re-import the
paragraph still has textAlign=center in the DB (was null before).

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

packages/git-sync/src/lib/docmost-schema.ts

@@ -238,7 +238,19 @@ const DocmostAttributes = Extension.create({
         attributes: {
           id: { default: null },
           indent: { default: null },
-          textAlign: { default: null },
+          // textAlign must round-trip the exported `<p style="text-align:…">`
+          // (and the legacy `<... align="…">`) form (review #10). Without an
+          // explicit parseHTML the default reads a bare `textAlign` attribute
+          // (never present), so alignment was silently dropped on every import.
+          textAlign: {
+            default: null,
+            parseHTML: (el: HTMLElement) =>
+              el.style?.textAlign || el.getAttribute("align") || null,
+            renderHTML: (attrs: Record<string, any>) =>
+              attrs.textAlign
+                ? { style: `text-align: ${attrs.textAlign}` }
+                : {},
+          },
         },
       },
       {

packages/git-sync/src/lib/markdown-converter.ts

@@ -97,7 +97,12 @@ export function convertProseMirrorToMarkdown(content: any): string {
         const text = nodeContent.map(processNode).join("");
         const align = node.attrs?.textAlign;
         if (align && align !== "left") {
-          return `<div align="${escapeAttr(align)}">${text}</div>`;
+          // Emit alignment as a styled `<p>` (review #10). The old
+          // `<div align="…">` had NO matching import parse rule — the div was
+          // unwrapped and alignment lost on every round trip. A styled `<p>`
+          // round-trips: the paragraph parse rule (tag:"p") matches and the
+          // textAlign global-attribute parseHTML (docmost-schema) reads the style.
+          return `<p style="text-align:${escapeAttr(align)}">${text}</p>`;
         }
         return text || "";