Section numerals: match the poster-closer headline treatment (#42)

01 / 02 / 03 section kickers were plain pink italic (`--accent-ink`).
Replaced with the same poster treatment used on
`.poster-closer__headline` ("Ship your AGENTS.md like it's code."):

- fill: `--poster-pink` (#ff79de)
- stepped dark drop-shadow: 8 offsets × 1px along the SE diagonal,
  colour `--poster-ink` (#0a0f1a)
- outline: `-webkit-text-stroke: 2px var(--poster-ink)`
- `paint-order: stroke fill` so the pink sits on top, stroke only
  shows as an outline around the letterform

Net effect: the numerals read as chunky 3D display type identical to
the hero wordmark + closer headline, pulling the three kickers into
the same poster language instead of floating as flat accent text.

Legibility/contrast argument: the dark stroke + dark stacked shadow
provide the visible edge, so the pink fill vs light background is
decorative, not load-bearing. axe measures foreground colour against
background; the previous treatment used `--accent-ink` (#c30a7a, the
contrast-safe pink) for this reason. Posterising with stroke + shadow
is the established pattern on this page, so consistency wins.

Author: PetriLahdelma

site/app/globals.css

@@ -840,9 +840,24 @@ main.landing {
   font-weight: 900;
   font-size: 72px;
   line-height: 0.85;
-  color: var(--accent-ink);
+  color: var(--poster-pink);
   letter-spacing: -0.04em;
   font-variation-settings: "SOFT" 100;
+  /* Match the `.poster-closer__headline` poster treatment: pink fill,
+     stepped dark drop-shadow, dark stroke on outside of the letterform.
+     `paint-order: stroke fill` puts the fill on top so the stroke only
+     shows as an outline, not a bleed. */
+  text-shadow:
+    1px 1px 0 var(--poster-ink),
+    2px 2px 0 var(--poster-ink),
+    3px 3px 0 var(--poster-ink),
+    4px 4px 0 var(--poster-ink),
+    5px 5px 0 var(--poster-ink),
+    6px 6px 0 var(--poster-ink),
+    7px 7px 0 var(--poster-ink),
+    8px 8px 0 var(--poster-ink);
+  -webkit-text-stroke: 2px var(--poster-ink);
+  paint-order: stroke fill;
 }
 .section-header__label {
   font-family: ui-monospace, SFMono-Regular, Menlo, monospace;