Editor type in rem: prosekit's px typography ignored the responsive root

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

style/main.css

@@ -38,11 +38,13 @@
 }
 
 :root {
-  /* the one brand color - everything else is neutral. Tuned for
-     legibility against near-black, distinct from the YES canvas's own
-     cyan/magenta/yellow so UI chrome never fights with it. */
-  --accent: #f0923c;
-  --accent-soft: rgba(240, 146, 60, 0.16);
+  /* the one brand color - everything else is neutral. A muted,
+     desaturated echo of the YES canvas's cyan ink: same family as the
+     canvas so chrome harmonizes with it, but dusty enough to read as a
+     quiet spot color on dark stock rather than compete. Legible
+     against near-black both as text and under #0a0a0a button text. */
+  --accent: #8ec2c0;
+  --accent-soft: rgba(142, 194, 192, 0.16);
 
   --paper: #0a0a0a;
   --paper-raised: #161616;
@@ -492,14 +494,60 @@ textarea:focus {
   box-shadow: 0 0 0 3px var(--accent-soft);
 }
 
-.prosekit-editor p {
+/* ProseKit's typography.css (loaded from esm.sh at mount time) sets
+   fixed px font sizes on .ProseMirror, so they ignore the responsive
+   root font-size. Re-state them in rem/em at the same proportions,
+   with .prosekit-editor prefixed so these win on specificity. */
+.prosekit-editor .ProseMirror p {
+  font-size: 1rem;
+  line-height: 1.5;
   margin: 0 0 0.6em;
 }
 
-.prosekit-editor p:last-child {
+.prosekit-editor .ProseMirror p:last-child {
   margin-bottom: 0;
 }
 
+.prosekit-editor .ProseMirror h1 {
+  font-size: 2.5rem;
+  line-height: 1.1;
+  margin: 0.9em 0 0.1em;
+}
+
+.prosekit-editor .ProseMirror h2 {
+  font-size: 1.875rem;
+  line-height: 1.3;
+  margin: 1.05em 0 0.13em;
+}
+
+.prosekit-editor .ProseMirror h3 {
+  font-size: 1.5rem;
+  line-height: 1.33;
+  margin: 0.9em 0 0.04em;
+}
+
+.prosekit-editor .ProseMirror h4 {
+  font-size: 1.25rem;
+  line-height: 1.3;
+  margin: 0.8em 0 0.05em;
+}
+
+.prosekit-editor .ProseMirror h5 {
+  font-size: 1.125rem;
+  line-height: 1.22;
+  margin: 0.78em 0 0.06em;
+}
+
+.prosekit-editor .ProseMirror h6 {
+  font-size: 1rem;
+  line-height: 1.25;
+  margin: 0.75em 0 0.06em;
+}
+
+.prosekit-editor .ProseMirror :is(h1, h2, h3, h4, h5, h6):first-child {
+  margin-top: 0;
+}
+
 .alt-submit {
   font-family: var(--sans);
   font-weight: 600;