Validate camera vector XYZ without rejecting unused native lanes

docs/camera-vector-validation-crash.md

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+# Camera validation crash after the archive merge
+
+`game-20260907-225258.stderr.log` exited at tick1016 in state/category500.
+The imported camera publication check rejected the skeleton root translation
+`[5.0928864, -1.535, -4.822083, -inf]`. All position and basis XYZ components
+were finite; only the translation's fourth stored lane was non-finite.
+
+The native-shaped camera vectors retain all four lanes, but camera distances,
+dot products, direction tests and final rendered positions use XYZ. See
+`skate-core/src/camera/vector_tracker.rs`, `compass.rs` and `subject_pose.rs`.
+The merge introduced validation of every stored lane, incorrectly making the
+unused lane fatal even though the existing camera accepts this representation.
+
+Publication validation now checks XYZ independently for each root column and
+each position/direction/motion vector. Invalid XYZ remains an error. No source
+vector is sanitized, and no offboard simulation or camera tracking is changed.
+The root check also no longer allocates a temporary flattened vector each tick.
+
+Validation: source inspection and compilation; no automated gameplay/tests run.