feat: vertical helix with projects bound to strands

Reshape the landing so each project anchors to a slot on one of the two
helix strands. Strand A = Projects (durable, in-production), strand B =
Innovations (experiments, prototypes). Cards alternate L/R based on the
strand's instantaneous position at the slot — strand identity is shown
by colour + badge, not by side.

Schema
- ALTER projects ADD strand TEXT NOT NULL DEFAULT 'A' CHECK ('A','B').
  Generated as drizzle/0001_*.sql.

Component
- New VerticalHelix.svelte replaces Helix.svelte on the landing.
- Slot Y = 120 + i * 240; period = 480, so each strand is at an extreme
  at every slot. Node sits at the strand's actual x; card hugs that side.
- Pulsing node halos and animated gradient stops give "alive" feeling
  without moving the strand geometry — projects stay anchored.
- prefers-reduced-motion disables the pulse.
- <760px: SVG hides, cards stack full-width.

Authoring
- /projects/new form gets a Project / Innovation radio picker.
- Seed adds an "DNA Scout" example on strand B so the helix renders with
  both strands populated on first boot.

Landing
- Hero shrinks (60vh, no helix backdrop) and gains a strand legend.
- Top 12 projects bind to the helix; "See all N →" appears if there's
  more.
- Posts band becomes compact (3 most recent), below the helix.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

drizzle/meta/_journal.json

@@ -8,6 +8,13 @@
       "when": 1779267485591,
       "tag": "0000_giant_mother_askani",
       "breakpoints": true
+    },
+    {
+      "idx": 1,
+      "version": "6",
+      "when": 1779268639045,
+      "tag": "0001_sturdy_mysterio",
+      "breakpoints": true
     }
   ]
 }