M1: UI-fit instrumentation + headless ui_fit_test + first overflow fixes

Add panel overflow instrumentation (record_panel_fit reading ImGui ScrollMax),
a forced layout-reference + debug-aware center split, and host harness commands
(uisize/uifit). New headless ui_fit_test drives the real Controllers + Audio
panels at reference resolutions with Debug details on and asserts no panel
overflows its assigned size; the Audio panel gains a demo mode so its richest
content renders without a live mirror.

Fixes from the measured overflow: widen the center column (was too narrow ->
horizontal overflow), merge the Controllers poll/round-trip tables and fold the
trigger line into the slot line, and make the center height split
Debug-details-aware (Video's height is mirroring-driven, not debug-driven, so a
static split can't serve both modes). Controllers + Audio now fit at 1920x1080
with max info. Video/Injection/Log fit is finalized at the end via the live
uifit harness (M1 stays open until then).

15/15 ctest.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

host/src/injection_panel.cpp

@@ -657,6 +657,7 @@ void InjectionPanel::draw(bool debug_details)
 
 	draw_hook_status(debug_details);
 
+	record_panel_fit("Injection");
 	ImGui::End();
 }