fix(cctv): read TranStar dir as the camera's side of the road, at low confidence

TranStar's `dir` field is the side of the freeway a camera sits on, not
the way it faces. TranStar's own map script (translateCameraDirection)
shows it as "Traffic closest to the camera is traveling": South is
eastbound, North westbound, West southbound and anything else
northbound. The live catalog agrees: I-10 cameras are North/South and
I-45 cameras East/West.

Treating `dir` as a high-confidence facing pointed most Houston cameras
across or away from the road they watch, and dropped the "estimated"
marking. Map it to the travel direction instead (S 90, N 270, W 180,
E 0) as a low-confidence prior with the low-confidence pose, and keep
the id-hash fallback for None or unknown values.

changelog.d/1125-houston-cctv-pack.md

@@ -4,6 +4,8 @@
   stills synthesized from each numeric camera id on `www.houstontranstar.org`,
   so a catalog field cannot steer the proxy off-host. Cameras without a
   snapshot id, and cameras outside Greater Houston, are dropped. TranStar's
+  `dir` field (the side of the freeway the camera sits on) seeds a
+  low-confidence heading along the nearest lanes' travel direction. TranStar's
   disclaimer prohibits redistribution and external framing without TxDOT's
   written permission, so the pack is off unless `CCTV_HOUSTON_ENABLED=1`.
   Opting in loads the 250 cameras nearest downtown, Uptown, the Medical