a source-patched firefox launcher, same seam as the camoufox guide

[feder-cr]

#3629 (handleCloudflareChallenge not working as intended) is the recurring one, and the built-in fingerprint injection plus handleCloudflareChallenge still leaves a JS-layer surface anti-bots read: native function .toString(), the CDP attach signature, chromium-shape risk weighting.

the seam to fix it already exists here. docs/guides/avoid_blocking_camoufox.ts already swaps the engine via launchContext.launcher = firefox + useFingerprints:false. this is the same shape with a different binary: point launchOptions.executablePath at a firefox 150 build patched at the c++ source level (canvas readback, webgl getParameter, font metrics, audio, navigator, system colors) and pass spoof config through launchOptions.firefoxUserPrefs. no js shim, no CDP signature, values come back through normal gecko paths. it's feder-cr/invisible_firefox, MPL-2.

opened a draft PR with a proposal doc that mirrors the camoufox guide.

honest caveats: the invisible_playwright wrapper is python so it doesn't drop into crawlee's TS; what's reusable is the firefox binary itself, launched from playwright-node exactly like the camoufox guide. it helps the fingerprint/engine layer only, not IP reputation or a Press & Hold once it fires. firefox via playwright has no CDP so CDP-specific paths stay chromium-only.

if a guide + example (alongside avoid_blocking_camoufox) is in scope i'll write it. if not, happy to close it.

[feder-cr]

opened a draft PR with the proposal doc: #3713

[barjin]

See #3713 (comment)