test(e2e): run the real detectors (BotD + FingerprintJS OSS) on CI

Instead of only our hand-rolled signal checks, load the actual MIT detection
libraries against the patched binary and assert it isn't flagged:
- BotD (the client-side bot detector FingerprintJS Pro itself uses): detect()
  must return bot=false (no automation/headless tell).
- FingerprintJS OSS: visitorId present and stable across two fresh launches
  with the same seed (drift = per-session entropy = a bot tell).

Hermetic: the libs are vendored (tests/vendor/, pinned, MIT) and served from a
localhost server — no external CDN (Firefox tracking-protection blocks it
anyway), no IP/network dependency, runs identically on a dev box and the GitHub
runner. Both green locally against firefox-9.

tests/vendor/README.md

@@ -0,0 +1,18 @@
+# Vendored detection libraries (test-only)
+
+These are upstream, unmodified, MIT-licensed browser-fingerprinting / bot-detection
+libraries, vendored so the detector e2e tests run **hermetically and identically**
+on a dev box and on a GitHub runner (no external CDN at test time — Firefox
+tracking-protection blocks the openfpcdn.io CDN anyway, and we want CI offline).
+
+They are served from a localhost HTTP server and loaded into the patched Firefox;
+the tests assert the REAL detectors don't flag the stealth build (BotD: `bot===false`)
+and that the fingerprint is stable (FingerprintJS: same `visitorId` across launches).
+
+| File | Package | Version | Source | License |
+|---|---|---|---|---|
+| `botd-2.0.0.esm.js` | `@fingerprintjs/botd` | 2.0.0 | https://cdn.jsdelivr.net/npm/@fingerprintjs/botd@2.0.0/dist/botd.esm.js | MIT |
+| `fingerprintjs-5.2.0.umd.min.js` | `@fingerprintjs/fingerprintjs` | 5.2.0 | https://cdn.jsdelivr.net/npm/@fingerprintjs/fingerprintjs@5.2.0/dist/fp.umd.min.js | MIT |
+
+Both are MIT (Copyright © FingerprintJS, Inc.). To update: download the pinned
+dist from jsdelivr, drop it here, and bump the version in the filename + this table.