feat(3d): gl1 shim M4+M6+M7 — GLU quadrics, production link, stub retired; 47/47 parity

- gl1_glu: gluCylinder/gluDisk/gluSphere per the SGI GLU reference
  tessellation (sin/cos phase, strip emission order, pole fans — Apple's
  GLU derives from the same source, so vertices match the goldens);
  emission goes through the public glBegin/glVertex entry points so
  quadrics record into display lists
- glLineWidth>1 one-time warning (browsers clamp to 1; affected coverage
  stays under the parity floor — zero floors.json overrides needed)
- production link site: build-kicad-target.sh now compiles wasm/gl1 from
  sources.txt and applies wrapped_symbols.txt --wrap flags (same manifests
  as the test harness); kicad_editor's RENDER_3D_OPENGL links against the
  real emulation layer instead of no-ops
- wasm/stubs/gl_ffp_stub.c deleted (role fully superseded; history in git)
- docs: 3d-regression README port-status section (floor-blind small
  geometry + line-width caveats), harness comments de-red-stated

Parity: 47/47 under the 0.02 floor, zero overrides. Native golden path
byte-identical to bb0e238 (whose gate ran green) — scenarios/, native/,
baseline/, manifest, floors, spec all untouched by the port.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

scripts/build-3d-webgl-test.sh

@@ -3,8 +3,8 @@
 # Build script for the 3D-renderer WebGL test harness (WASM).
 #
 # Builds the shared 3D scenarios (tests/3d-regression/scenarios) + real KiCad
-# 3D-viewer TUs against the FFP no-op stubs (wasm/stubs/gl_ffp_stub.c) — the
-# TDD red state for the OpenGL->WebGL port. Output: tests/apps/3d-webgl/.
+# 3D-viewer TUs against the wasm/gl1 GL1->WebGL2 emulation layer (the
+# OpenGL->WebGL port). Output: tests/apps/3d-webgl/.
 #
 # Requires the wxWidgets WASM build (scripts/build-wx-wasm.sh) and the sysroot
 # headers (boost/glm) in build-wasm/sysroot.
@@ -15,7 +15,7 @@
 #   ./scripts/build-3d-webgl-test.sh --debug      # Debug build with source maps
 #
 # Modeled on scripts/build-gal-webgl-test.sh (no shader-generation step — the
-# FFP renderer has no GLSL yet; the port will add one here).
+# gl1 shim's FFP uber-shader lives inline in wasm/gl1/src/gl1_shaders.cpp).
 #
 
 source "$(dirname "$0")/common/logging.sh"

scripts/kicad/build-kicad-target.sh

@@ -445,24 +445,36 @@ if [ "${APP_NAME}" = "occ_service" ]; then
 fi
 
 # 3D viewer: built by DEFAULT (BUILD_3D_VIEWER=ON). Opt out with BUILD_3D_VIEWER=OFF, which links the
-# 3D stubs instead. The 3D viewer renders with the GL-free CPU raytracer (RENDER_3D_RAYTRACE_RAM)
-# blitted to the canvas through a plain WebGL2 textured quad — no -sLEGACY_GL_EMULATION. KiCad's
-# fixed-function OpenGL renderer is still compiled (shared files reference it) but never executed on
-# WASM, so its FFP/GLU entry points are satisfied at link time by no-op stubs (gl_ffp_stub.c). The
-# KiCad CMake option KICAD_BUILD_3D_VIEWER_WASM stays OFF upstream; our build passes it explicitly.
-# See docs/features/fork-cleanup/10-3d-viewer.md.
+# 3D stubs instead. The default renderer is still the GL-free CPU raytracer
+# (RENDER_3D_RAYTRACE_RAM) blitted through a WebGL2 textured quad, but KiCad's fixed-function
+# OpenGL renderer (RENDER_3D_OPENGL) now links against the REAL GL1->WebGL2 emulation layer
+# (wasm/gl1, no -sLEGACY_GL_EMULATION): the shim implements the FFP-only entry points and
+# --wrap-intercepts the Emscripten-owned names it must observe (wasm/gl1/wrapped_symbols.txt).
+# Regression gate: tests/3d-regression (47 golden scenarios). The KiCad CMake option
+# KICAD_BUILD_3D_VIEWER_WASM stays OFF upstream; our build passes it explicitly.
+# See wasm/gl1/README.md and docs/features/fork-cleanup/10-3d-viewer.md.
 BUILD_3D_VIEWER="${BUILD_3D_VIEWER:-ON}"
 GL3D_LINK_FLAGS=""
 if [ "${BUILD_3D_VIEWER}" = "ON" ]; then
-    log_info "3D viewer ENABLED for WASM (BUILD_3D_VIEWER=ON)"
-    emcc -c -I"${STUBS_DIR}" "${STUBS_DIR}/gl_ffp_stub.c" -o "${STUBS_BUILD}/gl_ffp_stub.o"
-    GL3D_LINK_FLAGS="${STUBS_BUILD}/gl_ffp_stub.o"
+    log_info "3D viewer ENABLED for WASM (BUILD_3D_VIEWER=ON) — compiling wasm/gl1 FFP shim"
+    GL1_DIR="${PROJECT_ROOT}/wasm/gl1"
+    while IFS= read -r gl1_src; do
+        [ -n "${gl1_src}" ] || continue
+        em++ -c ${EXTRA_FLAGS} -pthread -std=c++20 \
+             -I"${GL1_DIR}/include" -I"${STUBS_DIR}" -I"${SYSROOT}/include" \
+             "${GL1_DIR}/src/${gl1_src}" -o "${STUBS_BUILD}/${gl1_src%.cpp}.o"
+        GL3D_LINK_FLAGS="${GL3D_LINK_FLAGS} ${STUBS_BUILD}/${gl1_src%.cpp}.o"
+    done < "${GL1_DIR}/sources.txt"
+    while IFS= read -r gl1_sym; do
+        [ -n "${gl1_sym}" ] || continue
+        GL3D_LINK_FLAGS="${GL3D_LINK_FLAGS} -Wl,--wrap=${gl1_sym}"
+    done < "${GL1_DIR}/wrapped_symbols.txt"
 fi
 
 # Multi-threaded CPU raytracer (mainline threading restored): link the main-thread
 # nanosleep->Asyncify-yield shim so the raw-thread raytracer joins (sleep_for busy-wait)
 # yield to the JS event loop instead of deadlocking on-demand pthread-Worker creation.
-# Mirrors the gl_ffp_stub pattern (compile to .o, add to the link). Shim:
+# Mirrors the wasm/gl1 pattern (compile to .o, add to the link). Shim:
 # wasm/shims/nanosleep_yield.c; its EM_ASYNC_JS yield is covered by env.__asyncjs__* in
 # scripts/common/asyncify-imports.txt.
 emcc -c -pthread "${PROJECT_ROOT}/wasm/shims/nanosleep_yield.c" -o "${STUBS_BUILD}/nanosleep_yield.o"