kiosk: pi-friendly compact mode + chromium 72 fallbacks

- Detect kiosk mode (localhost / ?kiosk=1) and add html.kiosk-mode
- Suppress 3D path-viewer in kiosk mode (Pi 3B too slow)
- Compact 1366x768 layout: 56px header, smaller jog grid, 4-col macros
  2-col status, 540px jog column
- Flex-gap fallbacks for Chromium 72 (header tabs, sys-btn, state-badge,
  ktab, sp-row, etc.) using "> * + *" margin-* rules
- Path-viewer: opaque WebGL canvas, ResizeObserver-gated render loop,
  no first-frame size flash
- Path-viewer renderer cleared properly on component teardown
- W axis row: W- | W+ | Probe XYZ | Probe Z (was W-|HomeW|W+|Probe)
- Running panel only for actual program execution (not jogging)
- Settings sectioned (Display+Units / Probing / G-code+Motion)
- Routed component now keep-alive across tab swaps
- FA4 -> FA6 webfonts

Makefile

@@ -68,7 +68,11 @@ update: pkg
 
 build/templates.pug: $(TEMPLS)
 	mkdir -p build
-	cat $(TEMPLS) >$@
+	# Use awk to ensure each template is followed by a newline so the
+	# next file's first line never gets glued onto the previous file's
+	# last line (some templates ship without a trailing newline, which
+	# would produce subtle Pug parse failures).
+	awk 'FNR==1 && NR>1 {print ""} {print} END{print ""}' $(TEMPLS) >$@
 
 node_modules: package.json
 	npm install && touch node_modules