perf(vishot): compress and downscale AVIF screenshots (#1598)

* perf(vishot-runner-electron): compress and downscale AVIF screenshots

The capture pipeline was emitting AVIF at default quality with no
resolution cap, so 4K displays produced ~800KB per screenshot (~42MB
total for the tamagotchi manual). Add quality 50, speed 6, and a
1920px max-width downscale — expected output drops to ~20-40KB each
with no visible quality loss for UI documentation.

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

* perf(docs): regenerate manual screenshots with compression

Re-capture all 27 tamagotchi manual screenshots using the new AVIF
pipeline settings (quality 50, max-width 1920px, speed 6).

Before: ~800KB per image, ~42MB total (4K @ default quality)
After:  ~15-38KB per image, ~1MB total (1920px @ quality 50)

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

---------

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

packages/vishot-runner-electron/src/cli/capture.ts

@@ -18,6 +18,13 @@ import { resolveElectronAppInfo } from '../utils/app-path'
 
 type CaptureFormat = 'png' | 'avif'
 
+/** Max width for AVIF output — anything wider is downscaled proportionally. */
+const AVIF_MAX_WIDTH = 1920
+/** AVIF quality (0-100, 100 = lossless). 50 is nearly indistinguishable for UI screenshots. */
+const AVIF_QUALITY = 50
+/** rav1e speed preset (1 = slow/best, 10 = fast/worst). 6 balances size vs encode time. */
+const AVIF_SPEED = 6
+
 interface CaptureCliArguments {
   scenarioPath: string
   outputDir: string
@@ -69,7 +76,20 @@ function createAvifTransformer(): ArtifactTransformer {
   return async (artifact) => {
     // eslint-disable-next-line e18e/prefer-static-regex
     const derivedFilePath = artifact.filePath.replace(/\.png$/i, '.avif')
-    const avifBuffer = await new Transformer(await readFile(artifact.filePath)).avif()
+
+    const transformer = new Transformer(await readFile(artifact.filePath))
+    const metadata = await transformer.metadata()
+
+    // Downscale images wider than AVIF_MAX_WIDTH, keeping aspect ratio
+    if (metadata.width > AVIF_MAX_WIDTH) {
+      const scale = AVIF_MAX_WIDTH / metadata.width
+      transformer.resize(AVIF_MAX_WIDTH, Math.round(metadata.height * scale))
+    }
+
+    const avifBuffer = await transformer.avif({
+      quality: AVIF_QUALITY,
+      speed: AVIF_SPEED,
+    })
 
     await writeFile(derivedFilePath, avifBuffer)
     await rm(artifact.filePath, { force: true })