Clips unfurl: share cards, faststart video, a share button

Each clip page already carried its own title, blurb, poster and
og:video — but the assets behind the tags let the unfurl down. The mp4s
were tail-indexed, so previewers in iMessage, Discord, Slack and
Facebook gave up before finding a player; the tags carried no video
dimensions, without which those same sites refuse to embed one; and the
poster was a 736x578 screenshot of the workshop chrome, cropped to
nothing by any share sheet.

deploy/clips-prep.mjs fixes the set before clips-publish.sh ships it:
a lossless faststart remux of every take, a 1200x630 card per clip cut
from the poster's first-person viewport with the title set over it (an
HTML card screenshot through the harness's chromium — ffmpeg here has
no drawtext), and the fpv frame size stamped into clips.json. The page
emits the card with its dimensions, og:video:width/height, and a Share
button that opens the phone's share sheet or copies the link.

Co-Authored-By: Claude Fable 5.1 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01Jm2auWk6RP71CjaAb4FMoG

deploy/clips-prep.mjs

@@ -0,0 +1,111 @@
+// Make a clips directory unfurl well before clips-publish.sh ships it:
+//   - remux every mp4 with its index up front (faststart). Previewers in
+//     iMessage, Discord, Slack and Facebook read the head of the file to
+//     decide whether to show a player, and give up on a tail-indexed one.
+//   - cut a 1200x630 share card per clip — the poster's first-person
+//     viewport, full-bleed, with the title set over it — for og:image.
+//     Share sheets crop anything that isn't 1.91:1; X crops to 2:1.
+//   - stamp each clip's video width/height into clips.json so the page
+//     can emit og:video:width/height, without which Facebook, LinkedIn
+//     and Discord refuse to embed a player.
+//
+//   npx tsx deploy/clips-prep.mjs <clips-dir>
+//
+// Needs ffmpeg + ffprobe and the Playwright chromium cache (see
+// verify-scenes.mjs). Idempotent: run it again after re-recording.
+import { execFileSync } from "node:child_process";
+import { existsSync, readdirSync, readFileSync, renameSync, unlinkSync, writeFileSync } from "node:fs";
+import { join } from "node:path";
+import { chromium } from "playwright-core";
+
+const dir = process.argv[2];
+if (!dir || !existsSync(join(dir, "clips.json"))) {
+  console.error("usage: clips-prep.mjs <clips-dir>   (a directory holding clips.json)");
+  process.exit(1);
+}
+
+// The workshop poster is a screenshot of the replay stage; the wizard's
+// viewport sits at this rectangle within it — a 16:9 window.
+const VIEWPORT = { x: 18, y: 51, w: 700, h: 393 };
+const CARD = { width: 1200, height: 630 };
+
+function chromiumExe() {
+  if (process.env.WIZWAR_CHROME) return process.env.WIZWAR_CHROME;
+  const cache = join(process.env.HOME ?? "", "Library", "Caches", "ms-playwright");
+  const builds = existsSync(cache)
+    ? readdirSync(cache).filter((d) => /^chromium-\d+$/.test(d)).sort()
+    : [];
+  for (const build of builds.reverse()) {
+    const exe = join(cache, build, "chrome-mac-arm64",
+      "Google Chrome for Testing.app", "Contents", "MacOS", "Google Chrome for Testing");
+    if (existsSync(exe)) return exe;
+  }
+  throw new Error("no Playwright chromium found — run: npx playwright-core install chromium (or set WIZWAR_CHROME)");
+}
+
+const ff = (...args) => execFileSync("ffmpeg", ["-loglevel", "error", "-y", ...args]);
+
+function faststart(file) {
+  const tmp = `${file}.tmp.mp4`;
+  ff("-i", file, "-c", "copy", "-movflags", "+faststart", tmp);
+  renameSync(tmp, file);
+}
+
+function videoSize(file) {
+  const [width, height] = execFileSync("ffprobe", ["-v", "error", "-select_streams", "v:0",
+    "-show_entries", "stream=width,height", "-of", "csv=p=0", file]).toString().trim().split(",").map(Number);
+  return { width, height };
+}
+
+const esc = (s) => s.replace(/&/g, "&amp;").replace(/</g, "&lt;");
+
+/** The share card: the viewport scaled to the card's width (a 16:9 crop
+ * runs 674 tall at 1200 wide, so 22px shave top and bottom), a shade
+ * rising from the bottom, the title in the gallery's gold over it. */
+function cardHtml(title, viewportPngDataUrl) {
+  return `<!doctype html><html><head><meta charset="utf-8"><style>
+    html, body { margin: 0; width: ${CARD.width}px; height: ${CARD.height}px; overflow: hidden; background: #171a21; }
+    .card { position: relative; width: ${CARD.width}px; height: ${CARD.height}px;
+            font-family: Georgia, "Times New Roman", serif; color: #d6d2c4; }
+    .card img { position: absolute; left: 0; top: -22px; width: ${CARD.width}px; height: 674px;
+                image-rendering: auto; }
+    .shade { position: absolute; inset: 0;
+             background: linear-gradient(to bottom, rgba(23,26,33,0) 45%, rgba(23,26,33,0.92) 100%); }
+    .title { position: absolute; left: 56px; right: 56px; bottom: 94px;
+             font-size: 66px; line-height: 1.1; color: #e8c87a; letter-spacing: 0.02em;
+             text-shadow: 0 2px 12px rgba(0,0,0,0.6); }
+    .mark { position: absolute; left: 58px; bottom: 52px; font-size: 26px; letter-spacing: 0.08em;
+            color: #d6d2c4; opacity: 0.9; text-shadow: 0 1px 8px rgba(0,0,0,0.6); }
+    .mark b { font-weight: normal; color: #e8c87a; }
+  </style></head><body><div class="card">
+    <img src="${viewportPngDataUrl}">
+    <div class="shade"></div>
+    <div class="title">${esc(title)}</div>
+    <div class="mark"><b>WIZ-WAR</b> &nbsp;·&nbsp; a clip from the labyrinth</div>
+  </div></body></html>`;
+}
+
+const clipsFile = join(dir, "clips.json");
+const clips = JSON.parse(readFileSync(clipsFile, "utf8"));
+const browser = await chromium.launch({ executablePath: chromiumExe() });
+const page = await browser.newPage({ viewport: CARD, deviceScaleFactor: 1 });
+try {
+  for (const clip of clips) {
+    for (const take of ["fpv", "board"]) faststart(join(dir, `${clip.name}-${take}.mp4`));
+    Object.assign(clip, videoSize(join(dir, `${clip.name}-fpv.mp4`)));
+
+    const crop = join(dir, `.${clip.name}-viewport.png`);
+    ff("-i", join(dir, `${clip.name}.jpg`),
+      "-vf", `crop=${VIEWPORT.w}:${VIEWPORT.h}:${VIEWPORT.x}:${VIEWPORT.y}`, crop);
+    const dataUrl = `data:image/png;base64,${readFileSync(crop).toString("base64")}`;
+    unlinkSync(crop);
+    await page.setContent(cardHtml(clip.title, dataUrl));
+    await page.evaluate(() => document.fonts.ready);
+    await page.screenshot({ path: join(dir, `${clip.name}-card.jpg`), type: "jpeg", quality: 88 });
+    console.log(`${clip.name}: ${clip.width}x${clip.height}, faststart, card`);
+  }
+} finally {
+  await browser.close();
+}
+writeFileSync(clipsFile, JSON.stringify(clips, null, 2) + "\n");
+console.log(`prepped ${clips.length} clips in ${dir}`);