feat(chat-bg): redesign 19 chat backgrounds as modular per-pattern files

Same treatment as the seasonal themes: split the 502-line chatBackground.ts Record into one premium module per background under lotus/backgrounds/ (each exposes a tuned dark + light ChatBgVariants), one Opus agent per background against a shared brief. chatBackground.ts now assembles DARK/LIGHT from the modules; getChatBg is unchanged. Carbon + Aurora are kept inline as-is (user favorites); none stays the empty layer. Every redesign: layered oklch palettes, seamless tiling with worked-out tile math (integer-multiple periods; edge-wrapping inline-SVG data-URIs for circuit/hexgrid/waves/herringbone/chevron/tactical), independently-tuned dark+light (not a recolor), and low "felt-not-read" opacity so chat text stays WCAG-AA legible. The 5 animated backgrounds (rain, star drift, grid pulse, aurora flow, fireflies) each colocate a vanilla-extract keyframe .css.ts, animate only background-position for a jump-free loop, and — since getChatBg strips animation for reduced-motion — render a finished static frame too. Redesigned: blueprint, stars, topographic, herringbone, crosshatch, chevron, polka, triangles, plaid, tactical, circuit, hexgrid, waves, neon, anim-rain, anim-stars, anim-pulse, anim-aurora, anim-fireflies. Gates: tsc clean, ESLint clean, Prettier clean, build OK, 551 tests pass. Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
2026-06-30 20:23:54 -04:00
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+import { keyframes } from '@vanilla-extract/css';
+
+// Fireflies — a slow, gentle PAN of sparse glowing motes across a warm summer
+// dusk. The scene in animFireflies.ts stacks these background layers:
+//   1. large bright motes  — tile 227x227, brightest core+halo, drifts FASTEST
+//   2. medium motes        — tile 293x293, dimmer, medium drift
+//   3. tiny far sparks     — tile 179x179, faintest, drifts SLOWEST (small step)
+//   4. center vignette      (100% 100%) — STATIC
+//   5. warm dusk wash A     (100% 100%) — STATIC
+//   6. warm dusk wash B     (100% 100%) — STATIC
+//
+// Seamless drift: the single `animation` shorthand shares ONE duration across all
+// layers, so the differing apparent speeds come purely from how FAR each layer
+// travels. For a jump-free loop every mote layer must translate by an EXACT
+// integer multiple of its own tile period in BOTH axes, so the mote re-entering
+// at the wrap is identical to the one that left. Each layer moves exactly one
+// full tile:
+//   large : -227 / -227  (1 x 227)
+//   medium: -293 / -293  (1 x 293)  — bigger tile, same 1-tile move => SLOWER look
+//   far   : -179 / -179  (1 x 179)  — smallest tile, damped by low opacity so it
+//                                     reads as the calm distant layer
+// Because tile sizes differ, one shared 1-tile translation yields three distinct
+// apparent speeds — the wandering-firefly parallax — while every layer lands back
+// on an identical phase at 100% for a perfectly seamless repeat.
+//
+// The diagonal component (both x and y shift) makes motes feel like they wander
+// through the meadow rather than slide flatly. The three static layers (vignette
+// and the two dusk washes) are pinned at '0 0' every frame so the warm ambient
+// glow and the calm reading center never move under the text.
+//
+// The '0%' frame MUST match the static backgroundPosition authored in
+// animFireflies.ts, so when getChatBg STRIPS this animation for
+// prefers-reduced-motion the finished scene of glowing motes shows without a jump.
+export const firefliesDrift = keyframes({
+  '0%': {
+    // large, medium, far, vignette, wash A, wash B
+    backgroundPosition: '0 0, 83px 47px, 131px 101px, 0 0, 0 0, 0 0',
+  },
+  '100%': {
+    // large: 0-227 / 0-227
+    // medium: 83-293 / 47-293
+    // far: 131-179 / 101-179
+    backgroundPosition: '-227px -227px, -210px -246px, -48px -78px, 0 0, 0 0, 0 0',
+  },
+});