feat(cards): add 'note' card type for readable markdown content

New card type renders body as styled markdown with no copy/fill/run
affordance. Glyph: ¶, color: --note.

Migration uses transaction to safely rebuild table constraint.
Checks both 'note' presence and modified_at column to catch
partial migration state.

web/app.js

@@ -4,14 +4,14 @@
   const GLYPHS = {
     note: '—', todo: '○', event: '◇', reminder: '△',
     snippet: '◆', template: '◈', checklist: '☐',
-    decision: '⚖', link: '↗',
+    decision: '⚖', link: '↗', note: '¶',
   };
 
   const GLYPH_CLASSES = {
     note: 'glyph-note', todo: 'glyph-todo', event: 'glyph-event', reminder: 'glyph-reminder',
     snippet: 'glyph-snippet', template: 'glyph-template',
     checklist: 'glyph-checklist', decision: 'glyph-decision',
-    link: 'glyph-link',
+    link: 'glyph-link', note: 'glyph-note',
   };
 
   const PAGE_SIZE = 50;
@@ -121,7 +121,7 @@
 
   // ========== Grammar parser (mirrors Go parser) ==========
 
-  const VALID_CARDS = { card: 'snippet', c: 'snippet', snippet: 'snippet', template: 'template', checklist: 'checklist', decision: 'decision', link: 'link' };
+  const VALID_CARDS = { card: 'snippet', c: 'snippet', snippet: 'snippet', template: 'template', checklist: 'checklist', decision: 'decision', link: 'link', note: 'note', n: 'note' };
 
   function validateTime(s) {
     const parts = s.split(':');