fix: stop Chrome downloading an on-device model on every browser start - #29

What changed

Two entries in default_arguments in botasaurus_driver/core/config.py:

• OptimizationHints added to the existing --disable-features list;
• --disable-background-networking added.

A fresh Chrome profile spends an idle window downloading the Optimization
Guide's on-device model from optimizationguide-pa.googleapis.com. Nothing in a
scrape reads it, and a driver that opens a new profile per task pays for it on
every start - which for anyone running through a metered residential proxy is
billed traffic for a file no target ever sees.

Measurement

2026-08-25, Windows 10, Chrome 149.0.7827.201, Driver(headless=True), 60 s
parked on about:blank with nothing navigated. Bytes counted at a loopback
CONNECT proxy and attributed per authority, so these are socket bytes rather
than anything a page-level hook reported.

Each flag was isolated before either was proposed, on the same setup:

--disable-component-update is the one that looks like it should help and does
nothing measurable, which is why it is not in this diff.

OptimizationHints is the master switch for the service. The narrower
OptimizationHintsFetching, OptimizationTargetPrediction and
OptimizationGuideModelDownloading do not work - I measured a library that
ships all three on its command line and fetches 24-30 MB anyway.

A caveat on reading these numbers: the fetch does not fire on every start. Seven
of eight unflagged runs fetched and one was quiet, so one quiet run proves
nothing. Every row above is one of two runs and the flagged ones are quiet in
both.

Fingerprint

Neither flag is visible to a page. 31 probes sampled from Driver with and
without them - the full navigator prototype property list (83 names), all 1232
window own-property names, plugins, mimeTypes, WebGL vendor, renderer and
extension list, userAgentData, Intl.resolvedOptions, screen metrics,
PerformanceObserver.supportedEntryTypes - come back identical.
--disable-background-networking is already shipped by default in zendriver,
SeleniumBase and Playwright, and patchright ships OptimizationHints.

Note on a related sharp edge

Config.browser_args returns sorted(self.default_arguments + self.arguments).
Because Chrome honours only the last occurrence of a repeated switch, a user who
passes their own --disable-features=... through arguments either wins or is
silently ignored depending on where their string sorts against
--disable-features=IsolateOrigins,.... Merging into the existing list, as this
diff does, avoids adding a second copy. Fixing the general case is a bigger
change and is not attempted here.