style(brand): unify orange to #FA7850 + yellow token; fix tablet header gap

- Brand orange is now the official #FA7850 everywhere: folded the stray
  oranges (#F2762E, #E8833A, #ff6b2c) into it and kept a single darker shade
  (#E85D2A) for gradient depth + button hover. Added the official brand
  --yellow (#FFE16E) token.
- Tablet header gap (769-1024px): the fixed header shrinks 80->60px there but
  first-section paddings kept their 80px clearance; pull the first section up
  by the 20px delta in that range only (phones untouched). Verified on
  interior pages and the full-bleed homepage hero — gap now matches desktop,
  no overlap.
- Re-stamped cache-bust (v=f95de694).

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

css/base/_typography.css

@@ -13,15 +13,14 @@
   --teal-600:    #255E73;   /* button hover */
   --teal-800:    #153C4E;   /* deep accents */
 
-  /* Brand — orange.  NOTE: the site currently ships two primary oranges:
-     --orange (event pages / logo family) and --orange-cta (homepage buttons).
-     They read as slightly different brands side by side; unify on one once the
-     canonical value is confirmed. */
-  --orange:      #F2762E;
-  --orange-600:  #E85D2A;
-  --orange-cta:  #FA7850;
+  /* Brand — orange (official: #FA7850, the single source of truth) */
+  --orange:      #FA7850;
+  --orange-600:  #E85D2A;   /* darker shade — gradients & button hover */
   --orange-text: #B4531A;   /* AA-safe orange for text on white */
 
+  /* Brand — yellow (official) */
+  --yellow:      #FFE16E;
+
   /* Ink / text */
   --ink:         #101828;
   --text:        #344054;