Move Odin renderer into gui/ with per-project Makefiles

Each sub-project (gui, api, infra) now owns its own Makefile, and the
root Makefile is a lean delegator for the base commands (run, build,
test, clean, fmt). Odin source, deps, and web assets live under gui/
(gui/src, gui/lib, gui/www), with scripts kept under gui/scripts for
build tooling only.

gui/scripts/build_web.sh

@@ -0,0 +1,54 @@
+#!/usr/bin/env bash
+# Builds the WebAssembly ("web") build of DESI Explorer with Odin
+# (js_wasm32) + emscripten. Output: build/web/index.html (+ index.wasm,
+# odin.js) at the repo root. Run via `make -C gui build-web`.
+#
+# Requires:
+#   - `odin` on PATH with the js_wasm32 target
+#   - emcc / emscripten active in PATH
+# Optional:
+#   - ODIN_ROOT (defaults to `odin root`)
+#   - OUT_DIR   (defaults to <repo>/build/web)
+set -euo pipefail
+
+# Resolve the gui/ project root so this script works regardless of CWD.
+SCRIPT_DIR="$(cd "$(dirname "${BASH_SOURCE[0]}")" && pwd)"
+GUI_DIR="$(cd "${SCRIPT_DIR}/.." && pwd)"
+ROOT_DIR="$(cd "${GUI_DIR}/.." && pwd)"
+
+OUT_DIR="${OUT_DIR:-${ROOT_DIR}/build/web}"
+ODIN_ROOT="${ODIN_ROOT:-$(odin root)}"
+
+mkdir -p "${GUI_DIR}/lib/local"
+mkdir -p "$OUT_DIR"
+
+# The Odin compiler emits a wasm object; raylib's C code is linked later by
+# emcc. `-define:RAYLIB_WASM_LIB=env.o` stops the compiler from trying to
+# link the raylib lib itself (emcc does that; it ends up in the final module).
+odin build "${GUI_DIR}/src" \
+  -target:js_wasm32 \
+  -build-mode:obj \
+  -define:RAYLIB_WASM_LIB=env.o \
+  -o:speed \
+  -collection:lib="${GUI_DIR}/lib/local" \
+  -out:"${OUT_DIR}/game"
+
+# Odin's JS runtime glue; the generated module imports functions from it.
+cp "${ODIN_ROOT}/core/sys/wasm/js/odin.js" "${OUT_DIR}/odin.js"
+
+# Link with emscripten against raylib's prebuilt web library. Flags mirror the
+# known-good karl-zylinski/odin-raylib-web template.
+emcc \
+  -o "${OUT_DIR}/index.html" \
+  "${OUT_DIR}/game.obj" \
+  "${ODIN_ROOT}/vendor/raylib/wasm/libraylib.web.a" \
+  --shell-file "${GUI_DIR}/www/index_template.html" \
+  -sEXPORTED_RUNTIME_METHODS="['HEAPF32']" \
+  -sUSE_GLFW=3 \
+  -sWASM_BIGINT \
+  -sWARN_ON_UNDEFINED_SYMBOLS=0 \
+  -sASSERTIONS
+
+rm -f "${OUT_DIR}/game.obj"
+
+echo "Web build created in ${OUT_DIR}"