build(solo-dual): optimise for size (-Os), not -Ofast

The nRF52 Arduino core compiles with -Ofast (≈ -O3 + -ffast-math) by
default, which had pushed this feature-rich solo build to ~90% flash.
Unflag -Ofast and build with -Os: flash drops 90.1% → 60.9% (638 KB →
431 KB, ~200 KB reclaimed) with no loss of functionality and a negligible
speed cost for a UI/mesh workload. -Os also avoids fast-math float
reassociation, so it's marginally safer for the geo/distance maths.

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

variants/wio-tracker-l1/platformio.ini

@@ -152,9 +152,15 @@ extra_scripts = post:create-uf2.py
 
 [env:WioTrackerL1_companion_solo_dual]
 extends = WioTrackerL1CompanionDual
+; Optimise for size, not speed: the nRF52 Arduino core defaults to -Ofast
+; (≈ -O3 + -ffast-math), which bloats flash by ~200 KB on this feature-rich
+; solo build. -Os keeps every feature, fits comfortably, and is actually safer
+; for float (no fast-math reassociation). Speed is irrelevant for the UI/mesh.
+build_unflags = -Ofast
 build_flags = ${WioTrackerL1CompanionDual.build_flags}
   -D UI_HAS_JOYSTICK_UPDOWN=1
   -D ENABLE_SCREENSHOT
+  -Os
 extra_scripts = post:create-uf2.py
 
 [env:WioTrackerL1_companion_dual_dev]