Move structural breakpoint to 640px, shorten Hero heading

Tablet layout (768-1023px) hit the md: grid switch exactly where the
fluid clamp() tokens were already at their floor, leaving no room to
shrink. Moves the fluid floor and structural breakpoint down together
to sm: (640px) so real tablets always get the fluid, desktop-like
structure; consolidates the ad-hoc md:+lg: patchwork in Hero/About/
Newsletter/Footer/Tools back onto one line, leaving documented lg:
exceptions where content genuinely doesn't fit yet. Also shortens the
Hero heading to a single sentence with no trailing period (the brand's
orange dot already renders one, animated).

app/components/Tools.tsx

@@ -30,23 +30,29 @@ export async function Tools() {
         </p>
       </Reveal>
 
-      {/* Tools grid — 3 cols md+, stacked below md; internal icon+text layout
-          stays horizontal at every size, only the outer span changes */}
-      <RevealGroup className="grid grid-cols-1 md:grid-cols-12 gap-10 md:gap-[var(--layout-grid-gap)] px-[var(--layout-padding-x)] w-full">
+      {/* Tools grid — 3 cols sm+ (moved down from the old md: so the grid
+          arrives where the fluid floor also sits), stacked below sm;
+          internal icon+text layout stays horizontal at every size, only
+          the outer span changes */}
+      <RevealGroup className="grid grid-cols-1 sm:grid-cols-12 gap-10 sm:gap-[var(--layout-grid-gap)] px-[var(--layout-padding-x)] w-full">
         {tools.map((tool) => (
           <RevealItem
             key={tool.id}
-            className="md:col-span-4 flex gap-8 items-start rounded-md transition-transform duration-300 hover:-translate-y-1"
+            className="sm:col-span-4 flex gap-8 items-start rounded-md transition-transform duration-300 hover:-translate-y-1"
           >
             {/* Icon — uniform box, pre-flipped/rotated source asset.
                 size-14 (56px) is a fixed value at every width (14 isn't
                 one of this project's fluid spacing-scale steps) — smaller
-                below md: so it doesn't dwarf the title/description text,
+                below lg: so it doesn't dwarf the title/description text,
                 which does shrink toward its own fluid floor there. Full
-                56px only from lg: up — at md: (Tablet, where this grid
-                already switches to 3-up) the title/description are still
-                fairly close to their own fluid floor, so the full-size
-                icon read as too big next to them too. */}
+                56px only from lg: up — a deliberate exception to the
+                site's sm: (640px) structural consolidation: the grid now
+                switches to 3-up at sm:, but title/description are still
+                fairly close to their own fluid floor through the whole
+                640-1023px range, so the full-size icon still reads too big
+                next to them there. Not re-verified visually — narrower
+                exception kept as-is, same reasoning as Hero's content
+                sizing. */}
             <div className="relative flex items-center justify-center shrink-0 size-11 lg:size-14">
               <Image alt="" src={tool.icon} fill sizes="(min-width: 1024px) 56px, 44px" className="object-contain" />
             </div>