fix(extension): mint reCAPTCHA via hidden widget — unblocks generate after the 2026-09-22 build

[Matro81]

Problem

Since frontend build boq_labs-ai-sandbox-frontend_20260922.00_p0 (deployed ~2026-09-22 16:45–17:52 UTC), every generate RPC this extension submits fails with PUBLIC_ERROR_UNUSUAL_ACTIVITY (grpc 7) — while clicking Generate in the Flow UI on the same tab still works. This is the break reported in #58.

The conclusion in #58 ("self-minted tokens are now rejected regardless") is not quite right: the constraint moved into how the token is minted, not into self-minting as such. A token obtained by calling grecaptcha.enterprise.execute(SITE_KEY, {action}) directly — the way injected.js did it — is now rejected. A token minted the way the page's own code does it (render a widget, execute the widget id) still passes.

Evidence (A/B, same account, same build, same project, 2026-09-24)

Path	Mint method	Result
FlowKit main (0.3.2)	execute(SITE_KEY, {action})	❌ UNUSUAL_ACTIVITY, 3/3 requests (each byte-compared against UI: sitekey/action/payload/headers identical)
Independent bridge (this PR's source)	ready() → render(hiddenDiv, {sitekey, size:'invisible'}) → execute(widgetId, {action})	✅ image completed, media_id e2f6fd77-02ff-4e7b-889e-403e370537b2
FlowKit + this patch (0.3.4)	same as above	✅ direct generate 4209e716-4155-45d8-8d89-c2392d333b6c; full pipeline (POST /api/requests → worker → scene row) 3bd7ff3b-ab16-461a-8194-e6fe267210d7, JPEG bytes verified from flow-content.google

What changed

extension/injected.js

• mintCaptcha() rewritten: resolveSitekey() reads the real sitekey off ___grecaptcha_cfg (hardcoded key kept as fallback) → enterprise.ready() → render an invisible widget into a hidden div → execute(widgetId, {action}), with retry. Mints stay serialized as before.

extension/content.js + 2 new bundled files

• flow.google.com no longer ships grecaptcha at page load, and its Trusted-Types CSP blocks <script src="https://www.google.com/…"> from the page. The only exempt route is the extension's own chrome-extension:// URL, so content.js preloads recaptcha_enterprise.js + recaptcha__en.js (same bundles as the reference bridge, byte-identical) into the MAIN world.
• Without this step the mint fails earlier with grecaptcha not available (hit exactly that while landing this fix).
• All injected script URLs carry ?v=<manifest.version> — Chrome was observed reusing a stale injected.js after a plain reload otherwise.

extension/manifest.json

• version 0.3.2 → 0.3.4 (forces a clean script fetch), both bundles added to web_accessible_resources.

Notes

• Uploads (maseQ) kept working through the break because MEDIA_UPLOAD was apparently not gated the same way — a useful, misleading data point for anyone triaging Every captcha-gated RPC returns PUBLIC_ERROR_UNUSUAL_ACTIVITY since the Flow frontend build of 2026-09-22, while the UI itself still works #58: a passing upload probe does not clear the mint path.
• After this fix, the only generate-path failures left should be genuine content moderation (PUBLIC_ERROR_UNSAFE_GENERATION, [3], 0 credits) — worth distinguishing in the retry policy from Harden Flow generation and restore project lifecycle #59's cooldown logic so moderation rejections don't look like a captcha regression.

Refs #58

[biziroyce]

@Matro81 it did work for a few hours, then, it does not work anymore. At this time of commenting, it does not work for me.