fix(A7): port retail calc_point_light (1-dist/falloff) ramp — kill the "spotlight" hard edge (#133)

The dungeon/house/outdoor lights read as hard-edged blown discs ("spotlights")
because our point/spot shader used `atten = 1.0` flat inside a hard `d < range`
cutoff. The mesh.frag comment claimed this was retail-faithful ("no attenuation
inside Range... the bubble-of-light look relies on crisp boundaries", citing
r13 10.2) — that was a misread and the literal cause of the symptom.

Verified against the decomp (not guessed): calc_point_light (0x0059c8b0, the
PER-VERTEX point-light path that lights static walls) scales each light's
contribution by (1 - dist/falloff_eff) — a LINEAR ramp that fades to exactly 0
at the edge, eliminating the hard disc. falloff_eff = Falloff * static_light_factor,
and static_light_factor = 1.3 (0x00820e24), NOT the 1.5 config_hardware_light
rangeAdjust (that 1.5 is the D3D-dynamic path for moving objects, a different
path). The Ghidra port (acclient.c:808639) is more garbled — BN pseudo-C is the
oracle here; the exact normalization factor + a half-Lambert wrap (0.5*dist+N*L)
are x87-obscured (same artifact class as GetPowerBarLevel) and left unported.

Changes:
- mesh_modern.frag + mesh.frag: replace flat atten with clamp(1 - d/range, 0, 1);
  Range now carries falloff_eff so the ramp fades to 0 at the cutoff. Fix the
  false "no attenuation / crisp bubble" comment in mesh.frag.
- LightInfoLoader: Range = Falloff * 1.3 (static_light_factor), was * 1.5.
- LightManager: correct the stale class doc comment (Tick is now nearest-8
  allocation-free partial-select with NO viewer-range slack filter).
- divergence register: AP-16 updated (slack filter removed), AP-35 added
  (per-pixel vs per-vertex Gouraud; dropped half-Lambert wrap + normalization).
- test: LightingHookSinkTests Range 8*1.3 = 10.4.

Build + 20 lighting tests green. Visual gate pending (game-wide lighting change:
dungeon torches, house candles, outdoor braziers).

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

src/AcDream.App/Rendering/Shaders/mesh_modern.frag

@@ -49,7 +49,15 @@ vec3 accumulateLights(vec3 N, vec3 worldPos) {
             if (d < range && range > 1e-3) {
                 vec3 Ldir = toL / max(d, 1e-4);
                 float ndl = max(0.0, dot(N, Ldir));
-                float atten = 1.0;
+                // Retail per-vertex point-light ramp (calc_point_light 0x0059c8b0,
+                // line 0x0059c9a2): contribution scales by (1 - dist/falloff_eff), a
+                // LINEAR fade to exactly 0 at the edge. That is what makes a torch a
+                // smooth glow that blends into the ambient instead of a flat disc with
+                // a hard edge — the dungeon/house/outdoor "spotlight" look (#133 A7).
+                // falloff_eff = Falloff * static_light_factor (1.3, 0x00820e24) is folded
+                // into the shader Range (dirAndRange.w) by LightInfoLoader, so the ramp
+                // denominator is just Range and fades to 0 exactly at the cutoff.
+                float atten = clamp(1.0 - d / max(range, 1e-3), 0.0, 1.0);
                 if (kind == 2) {
                     float cos_edge = cos(uLights[i].coneAngleEtc.x * 0.5);
                     float cos_l    = dot(-Ldir, uLights[i].dirAndRange.xyz);