#114265 secondary finding 1: ``network.force_ipv4`` was undiscoverable (default
off, mentioned only by a rotating tip), so an advertised-but-blackholed IPv6
prefix cost the reporter weeks. ``hermes doctor`` now runs an ``IPv6 route``
probe in the API Connectivity section: one 2 s IPv6 TCP connect to a known
dual-stack host. A timeout is the dead-route signature and is reported as a
warning plus a summary issue naming ``network.force_ipv4: true``; no AAAA /
no IPv6 route at all is healthy (fails fast, no stall) and ``force_ipv4``
already set skips the probe. Two invariant tests over a mocked connect seam.
Docs: doctor reference and the network config section describe the check.
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