maxProviderTimeoutMs top-level constant

Parses one connectTimeoutMs/streamIdleTimeoutMs field from a registry-entry node (issue #1398): null/absent → null; a positive integer within the sanity bound → the duration; anything else → ConfigException naming the field and the entry it lives on (strict, like every other config field — a typo must never silently keep the default).

Upper bound (maxProviderTimeoutMs, 1 h): a fat-fingered streamIdleTimeoutMs: 1800000 would parse fine and quietly disable the watchdog this config exists to provide — healthy glm-5.3-flash inter-chunk gaps peak around 200 s, so anything past the bound can never fire and is a config error, not a tuning choice.