Fix mouse look swallowing by the HUD

Move guard look handling to the _input stage, recapture the cursor on
window-focus return and when clicking back into gameplay, and make HUD controls
mouse-transparent. Add regression tests for yaw/pitch and HUD mouse filters.
Verified under Xvfb with real relative mouse motion. Headless 237/237, Python
94/94, movement smoke 60 fps.

CHANGELOG.md

@@ -4,6 +4,17 @@ All notable user-facing changes to Gig Line. The format follows
 [Keep a Changelog](https://keepachangelog.com/en/1.1.0/), and versions use
 Semantic Versioning.
 
+## [0.7.3] — 2026-11-01
+
+### Fixed
+
+- Mouse look now reads relative motion at the `_input` stage, so a full-screen
+  HUD or focused control cannot swallow it while the cursor is captured.
+- Mouse capture is restored after window/compositor focus returns, and clicking
+  back into a gameplay window recaptures it instead of opening the radial menu.
+- The HUD is mouse-transparent; its presentation controls no longer block
+  gameplay mouse input.
+
 ## [0.7.2] — 2026-11-01
 
 ### Added