build+perf: wasm-opt the shipped wasm, and measure real frames in CI

emcc only runs Binaryen at link -O2+ (link.py: should_run_binaryen_optimizer
returns OPT_LEVEL >= 2) and we link at -O1, so the shipped module had never seen
wasm-opt at all — it kept its entire 19.56 MB name section, ~20% of the editor
(-sJSPI sets ASYNCIFY=2, which suppresses wasm-ld's --strip-debug, leaving
wasm-opt as the only thing that would drop it). Step 8.2 runs it post-link and
in-container, so CI's cached compile phase covers it and the host post-process
stays pure-host.

Default -O2, picked by measuring every level on the same module: -O0 already
captures 27% of the raw win (it is mostly the name section), -O2 costs 23 s and
gives the best frame rate, and -O3/-O4/-Os/-Oz cost 48-132 s for at most 1.5%
more brotli — -O4 is not even smaller than -O3. Targets that already link -O2/-Oz
(occ_service, kicad_tools) are skipped by testing for the target_features
section, which emcc strips whenever it ran the optimizer itself, so there is no
hard-coded target list to drift. Feature flags come from the module's own
target_features section and so cannot diverge from the link.

The perf specs reported requestAnimationFrame ticks as "FPS". That is not a frame
rate: rAF fires on the compositor's schedule whether or not the GAL redrew, and
it read 120/s on a board where the renderer completed zero frames in six seconds.
measureInteractionFps now counts completed GAL frames — runs of draws to the
default framebuffer, exactly one per frame in every AA mode — and drives a pure
middle-drag pan after a zoom-to-fit. Mixing wheel zoom into the drive made the
result depend on where the wheel left the view: +-20% across identical repeats,
against +-2% for pan alone. The report gains a GAL fps column with a regression
flag on the 1x number; rAF is kept so historical runs stay comparable.

CI has no GPU, so its number is a software-rasteriser redraw rate — a regression
signal, not a user-facing frame rate. Method and measurements in the bench report.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_016X9eh1s5sTx1o9Em9KBuwR

scripts/build-monitor.sh

@@ -98,6 +98,7 @@ BEGIN {
     ord[++ROWN] = "kicad-configure"; lab["kicad-configure"] = "KiCad configure (CMake)"
     ord[++ROWN] = "kicad-compile";   lab["kicad-compile"]   = "KiCad compile"
     ord[++ROWN] = "kicad-bitmaps";   lab["kicad-bitmaps"]   = "Bitmap resources"
+    ord[++ROWN] = "wasm-opt";        lab["wasm-opt"]        = "wasm-opt (Binaryen)"
     ord[++ROWN] = "copy-output";     lab["copy-output"]     = "Copy output"
     ord[++ROWN] = "env-shim";        lab["env-shim"]        = "ENV merge shim"
     for (i = 1; i <= ROWN; i++) ridx[ord[i]] = i