gpsd-knowledge-patch

# gpsd Knowledge Patch Baseline: gpsd through 3.25; covers later releases through the latest documented state, including the 3.27.6 development stream. Use this skill for daemon deployment, protocol consumers, libgps clients, receiver configuration, PPS/NTP/chrony integration, capture and replay, and post-processing. Read the task-specific reference before relying on defaults or wire formats. ## Reference index | Reference | Topics | |---|---| | [Daemon architecture](references/daemon-architecture.md) | Device lifecycle, hotplug protocol, sniffing and drivers, normalized state, exporters, privilege boundaries | | [Daemon operation](references/daemon-operation.md) | Source URLs, serial framing, passive/nowait modes, control socket, D-Bus, time sources, client timeouts | | [Installation and building](references/installation-and-building.md) | SCons, dependencies, install layout, minimal and cross builds, permissions, udev, tests | | [JSON protocol](references/json-protocol.md) | Framing, VERSION/WATCH/POLL/DEVICE, TPV/SKY/GST/ATT/IMU/PPS, RTCM, AIS, SUBFRAME | | [Client programming](references/client-programming.md) | libgps C API, buffering, shared memory, gpsmm, Python binding, endpoints, units | | [Receiver hardware and control](references/receiver-hardware-and-control.md) | gpsctl, direct access, binary commands, PPS transport, firmware and device-specific setup | | [ubxtool](references/ubxtool.md) | Protocol versions, configuration layers, persistence, logging, survey-...