[Bug]: Docker pool's permanent browser never serves any request - signature is computed without the egress proxy, so no `/crawl` can ever match it

Summary

Found while investigating #2202. The Docker server's "permanent" warm browser is dead weight: it is started at boot, serves zero requests, is never cleaned up, and causes every container to run a second browser tree from the first request onward.

Root cause

The pool matches requests to browsers by hashing the full BrowserConfig (crawler_pool.py:46-49), and proxy_config is part of to_dict() (async_configs.py:968).

• init_permanent() is called at startup with a config built straight from config.yml — without enforce_egress() (server.py:199-203), so its fingerprint has proxy_config: None.
• Every /crawl request's config goes through enforce_egress() first (api.py:687-690), which sets proxy_config to the egress pinning proxy — whose port is random each boot (egress_broker.py:198-201).

The two fingerprints can never be equal, so _is_default_config() (crawler_pool.py:60) never matches and PERMANENT is never returned. Note get_default_browser_config() (server.py:126-141) does apply enforce_egress, so even the server's own /html, /screenshot, /pdf, /execute_js endpoints miss it.

Additionally, the janitor only sweeps HOT_POOL and COLD_POOL (crawler_pool.py:177,198) — PERMANENT is never inspected, so the unused browser also can never be reclaimed.

Impact

• ~270 MB RSS + one Playwright driver + full Chromium tree per container, doing nothing, forever.
• Every container shows two driver → browser process branches after the first request (observed in #2202's process listing: one branch from boot, one from the first crawl a day later).
• The text_mode optimization configured for the default browser never applies to real traffic.

Verified

Reproduced on unclecode/crawl4ai:0.9.2: fresh container = one browser tree; after a single plain /crawl = two independent trees, permanent one idle.

Proposed fix

Keep the permanent browser, fix the match: build its config through the same path requests use (get_default_browser_config(), i.e. after enforce_egress), and compute DEFAULT_CONFIG_SIG from that. Alternatively/additionally, exclude the server-injected proxy_config from the pool signature, since the server sets it identically on every request.

Start with crawler_pool.py:46-49, 60, 177, and 198, then trace the permanent-browser setup in server.py:126-141 and 199-203 and request handling in api.py:687-690. Verify that the permanent browser uses a matching request signature, serves the default traffic, and is included in janitor cleanup without creating a second browser tree.