refactor: modularize app.js into ES module architecture

Split the monolithic 5393-line app.js into 32 focused ES modules under
modules/ with a thin ~330-line orchestrator. No bundler required — runs
in-browser via import maps.

Module structure:
  core/     — scene, ticker, state, theme, audio
  data/     — gitea, weather, bitcoin, loaders
  terrain/  — stars, clouds, island
  effects/  — matrix-rain, energy-beam, lightning, shockwave, rune-ring, gravity-zones
  panels/   — heatmap, sigil, sovereignty, dual-brain, batcave, earth, agent-board, lora-panel
  portals/  — portal-system, commit-banners
  narrative/ — bookshelves, oath, chat
  utils/    — perlin

All files pass node --check. No new dependencies.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

modules/portals/commit-banners.js

@@ -0,0 +1,62 @@
+// modules/portals/commit-banners.js — Floating commit banner sprites
+import * as THREE from 'three';
+import { fetchRecentCommitsForBanners } from '../data/gitea.js';
+
+const commitBanners = [];
+
+function createCommitTexture(hash, message) {
+  const canvas = document.createElement('canvas');
+  canvas.width = 512; canvas.height = 64;
+  const ctx = canvas.getContext('2d');
+  ctx.fillStyle = 'rgba(0, 0, 16, 0.75)'; ctx.fillRect(0, 0, 512, 64);
+  ctx.strokeStyle = '#4488ff'; ctx.lineWidth = 1; ctx.strokeRect(0.5, 0.5, 511, 63);
+  ctx.font = 'bold 11px "Courier New", monospace'; ctx.fillStyle = '#4488ff'; ctx.fillText(hash, 10, 20);
+  ctx.font = '12px "Courier New", monospace'; ctx.fillStyle = '#ccd6f6';
+  const displayMsg = message.length > 54 ? message.slice(0, 54) + '\u2026' : message;
+  ctx.fillText(displayMsg, 10, 46);
+  return new THREE.CanvasTexture(canvas);
+}
+
+export async function init(scene) {
+  const commits = await fetchRecentCommitsForBanners();
+  const spreadX = [-7, -3.5, 0, 3.5, 7];
+  const spreadY = [1.0, -1.5, 2.2, -0.8, 1.6];
+  const spreadZ = [-1.5, -2.5, -1.0, -2.0, -1.8];
+  commits.forEach((commit, i) => {
+    const texture = createCommitTexture(commit.hash, commit.message);
+    const material = new THREE.SpriteMaterial({ map: texture, transparent: true, opacity: 0, depthWrite: false });
+    const sprite = new THREE.Sprite(material);
+    sprite.scale.set(12, 1.5, 1);
+    sprite.position.set(spreadX[i % spreadX.length], spreadY[i % spreadY.length], spreadZ[i % spreadZ.length]);
+    sprite.userData = {
+      baseY: spreadY[i % spreadY.length],
+      floatPhase: (i / commits.length) * Math.PI * 2,
+      floatSpeed: 0.25 + i * 0.07,
+      startDelay: i * 2.5,
+      lifetime: 12 + i * 1.5,
+      spawnTime: null,
+      zoomLabel: `Commit: ${commit.hash}`,
+    };
+    scene.add(sprite);
+    commitBanners.push(sprite);
+  });
+}
+
+export function update(elapsed) {
+  const FADE_DUR = 1.5;
+  commitBanners.forEach(banner => {
+    const ud = banner.userData;
+    if (ud.spawnTime === null) {
+      if (elapsed < ud.startDelay) return;
+      ud.spawnTime = elapsed;
+    }
+    const age = elapsed - ud.spawnTime;
+    let opacity;
+    if (age < FADE_DUR) opacity = age / FADE_DUR;
+    else if (age < ud.lifetime - FADE_DUR) opacity = 1;
+    else if (age < ud.lifetime) opacity = (ud.lifetime - age) / FADE_DUR;
+    else { ud.spawnTime = elapsed + 3; opacity = 0; }
+    banner.material.opacity = opacity * 0.85;
+    banner.position.y = ud.baseY + Math.sin(elapsed * ud.floatSpeed + ud.floatPhase) * 0.4;
+  });
+}