feat: highlight search matches and document the working UI

tools/desktop-capture/README.md

@@ -0,0 +1,60 @@
+# Real-engine desktop screenshots
+
+This independent software-test runner launches its own bundled headless Chromium
+with CPU rendering/video-decode flags. It does not control the user's Chrome,
+reuse personal profiles, or use Windows UI Automation. Screenshots render the
+production frontend against the actual shared Rust/Google EmbeddingGemma 2 engine;
+responses are neither replayed nor supplied by page evaluation.
+
+Playwright 1.64.0 is pinned in the package lock. See the official
+[browser installation](https://playwright.dev/docs/browsers) and
+[screenshot API](https://playwright.dev/docs/screenshots). The browser binaries
+stay under this tool's ignored node_modules directory.
+
+## Prepare
+
+Build the production frontend from apps/desktop with `npm ci && npm run build`.
+Build/stage the CPU Google worker and verified media helpers as documented in
+[BUILDING](../../docs/BUILDING.md). Provision the actual Google models first.
+The backend uses a dedicated generated/verified fixture corpus, never a user
+home/document directory. It indexes documents and two licensed real photos,
+then warms its retained CPU worker before listening on 127.0.0.1:1431.
+
+```powershell
+$env:SEARCHI_FORCE_CPU = '1'
+cargo run --manifest-path tools/desktop-capture/backend/Cargo.toml -- --root .searchi/readme-capture/files --db .searchi/readme-capture/index.sqlite --models .searchi/models/embeddinggemma2 --worker .searchi/runtime/cpu/Release/searchi-gemma-worker.exe --dist apps/desktop/dist --ffmpeg .searchi/media-runtime/bin/ffmpeg.exe --ffprobe .searchi/media-runtime/bin/ffprobe.exe
+```
+
+Keep that owned test process running while capturing. Its loopback API is a
+fixture-only test adapter with origin/token checks, not a product HTTP server.
+The production Tauri app keeps its native command/asset-protocol interface.
+
+In another terminal, from the repository root:
+
+```powershell
+npm ci --prefix tools/desktop-capture
+$env:PLAYWRIGHT_BROWSERS_PATH = '0'
+npm run --prefix tools/desktop-capture install-browser
+npm run --prefix tools/desktop-capture capture
+```
+
+The runner always uses the local browser cache and its own temporary profile.
+CPU flags are `--disable-gpu --disable-accelerated-video-decode --disable-webgl`.
+Only loopback fixture origin requests are permitted during capture. It waits for
+actual backend readiness, measured hybrid responses, matching DOM results,
+loaded fonts, image pixels, and genuine worker inference counters in debug mode.
+
+## Artifacts and limits
+
+Outputs under docs/screenshots are search-light.png, search-dark.png,
+media-search.png and performance-details.png, plus capture-manifest.json. The
+manifest contains actual fixture queries, counts/selection, measured response
+metrics, device/model, viewport, PNG SHA256, runner/browser versions, Git base
+commit and dirty-state flag. The base commit does not identify uncommitted
+source exactly. The ephemeral API token is never saved in the manifest.
+
+Captures are **browser-rendered production UI with the actual CPU engine**.
+They omit native window chrome. They do not establish native WebView visual QA,
+OS integration, playback codec parity, production relevance, GPU behavior or
+other operating-system releases. The runner closes only its browser; stop only
+the separately launched owned backend when finished.