fix: run correctly on modern Emscripten + release-grade performance flags (~15x less CPU)

[zackarychapple]

Summary

This port no longer builds or runs correctly on current Emscripten (tested with 6.0.2): compilation fails under the new clang's C23 default, and once that is worked around, a latent ABI bug corrupts memory at runtime (garbled 3D view, phantom "Player 4 left the game" messages, wrong HUD). This PR fixes both, migrates index.html to the current runtime APIs, and replaces the debug-grade build flags that were shipping in release builds.

Correctness

• boolean was a different size in different translation units (src/doomtype.h): TUs that had already included <stdbool.h> (via SDL headers) got a 1-byte bool; the rest got a 4-byte enum. Four-byte stores to globals like netgame clobbered the three adjacent bytes — corrupting playeringame[], the deathmatch flag, and renderer view state. Found with an Emscripten -fsanitize=address build (global-buffer-overflow WRITE on netgame). boolean is now unconditionally bool, and spriteframe_t.rotate becomes int (it uses memset(-1) as an uninitialized marker, which a 1-byte bool can't hold). Note: this changes struct layouts, so old savegames/demo recordings are incompatible.
• -std=gnu99: modern clang defaults to C23, where true/false are keywords and collide with the boolean enum.
• -fno-strict-aliasing: the id-era code type-puns byte buffers through int16/int32 pointers; don't let -O3 exploit that UB.
• STACK_SIZE=5MB: Emscripten's default shrank from 5 MB to 64 KB in 3.1.25; Doom's init path overflows the new default.
• index.html: FS.createPreloadedFile → Module.FS_preloadFile, and Module.arguments instead of the no-longer-exported callMain; added handlers so wasm crash stacks reach the console instead of vanishing as unhandled rejections.

Performance

• Removed debug flags from the release build: SAFE_HEAP=1 (instruments every memory access), STACK_OVERFLOW_CHECK=1, -g/-gsource-map. Added --closure 1 for the JS glue.
• Stopped Asyncify-sleeping on the frame hot path (src/d_loop.c, src/doom/d_main.c): the rAF main loop (60–120 Hz) outpaces the 35 Hz tic rate, so TryRunTics and the screen-wipe loop hit emscripten_sleep(1) on almost every frame — a full Asyncify stack unwind/rewind each time. They now return to the browser event loop instead; Asyncify stays for startup/netgame paths.
• Deliberately not -flto: at -O3 it compiles UB in this codebase into an unconditional trap in main() (verified; documented in configure.ac).

Before / after

Both builds use the same source (including the correctness fixes — the original code can't run at all on this toolchain) and the same Emscripten 6.0.2; "before" uses the original flag set, "after" this PR's. Measured on an Apple-Silicon Mac, headless Chrome, shareware doom1.wad.

Metric	Before	After	Δ
Main-thread wasm CPU during demo1 playback (10 s sampling profile)	1007 ms	68 ms	~15x less
Main-thread non-idle time	14.2%	5.6%	−61%
-timedemo demo1 (5198 gametics, display-capped)	1985 realtics (91.7 fps)	1814 realtics (100.3 fps)	−8.6% wall clock
JS glue size	197,487 B	79,809 B	−60%
wasm size	2,361,788 B	2,217,087 B	−6%
Source map shipped	1,381,684 B	0	eliminated

The CPU numbers are the meaningful ones: both builds are display-cap-bound on a fast desktop, but the before-build burns ~15x the CPU for the same frames — the gap that shows up as dropped frames and battery drain on phones and slower machines.

Manual Testing

1. ./scripts/clean.sh && ./scripts/build.sh (brew emscripten 6.0.2 + automake).
2. Copy shareware doom1.wad into src/, then cd src && python3 -m http.server 8000.
3. Open http://localhost:8000 — expected: title screen and attract demo render correctly.
4. Press a key → menu; Enter through New Game → E1M1 starts with the melt wipe; move/turn/strafe — expected: clean rendering, no "Player N left the game" messages, single-player ARMS HUD (not the FRAG counter), smooth input.
5. Verified end-to-end via CDP-driven Chrome (simulated keyboard input + screenshots) and an -fsanitize=address build running clean.

🤖 Generated with Claude Code

Deployed and playable at https://t-web-latest-zackary-chapple-doom-wasm-doom-wasm-zack-ef80f1-ze.zephyrcloud.app/