fix(assets): tune fog shader alpha and add zone temperature tint per D-059

Ticket #563. Light fog alpha tuned to 0.25-0.35 range (was 0.25-0.55),
deep fog alpha set to 0.55-0.70 with zone temperature tint from
zone_tint_tex (bar=warm #2a1f15, hub=cool #1a1f2e, corridor=neutral
#1a1a1a). Two Perlin noise cycles: 8-10s light, 15-20s deep.
Zone tint texture now populated per-tile from server zone_id in
fog_state.gd with preservation across texture resizes.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

client/shaders/fog.gdshader

@@ -1,9 +1,14 @@
 shader_type canvas_item;
 
-// D-059: 3-layer fog shader. Composites over world content.
-// Layer 1: Clear (forward cone) — transparent, soft gradient edge
-// Layer 2: Explored fog — light overlay indicating "not fresh", art preserved
-// Layer 3: Unexplored — solid near-black #12141a
+// D-059: 3-state fog shader (simplified from 5-layer by #569).
+// State 1: Clear (forward cone) — transparent, soft Gaussian gradient edge (6-8 tile spread)
+// State 2: Explored (out of cone, EXP_EXPLORED) — two sub-zones by vis proximity:
+//   a) Light fog (near cone gradient): alpha 0.25-0.35, neutral dark, 8-10s breathe
+//   b) Deep fog (far from cone, vis≈0): alpha 0.55-0.70, zone temperature tint, 15-20s breathe
+// State 3: Unexplored — solid near-black #12141a
+// D-033: Entity colors are NOT affected — they render above the fog overlay (z-layer 5).
+// D-046: Zone temperature tint from zone_tint_tex — warm=bar, cool=hub, neutral=corridor.
+// D-077: zone_tint_tex populated per-tile from server zone_id via fog_state.gd.
 
 uniform sampler2D visibility_tex : filter_linear, repeat_disable;
 uniform sampler2D exploration_tex : filter_linear, repeat_disable;
@@ -17,10 +22,10 @@ uniform float tile_size;     // Pixels per sim tile
 uniform float time;          // Seconds since start
 
 const vec3 UNEXPLORED_COLOR = vec3(0.071, 0.078, 0.102);  // #12141a
-const vec3 DARK_OVERLAY = vec3(0.02, 0.02, 0.05);
+const vec3 DARK_OVERLAY = vec3(0.02, 0.02, 0.05);         // neutral dark (light fog zone)
 
 // Soft gradient via 7x7 Gaussian blur on visibility (sigma 2.0).
-// Spreads the cone boundary into a 3-4 tile radius gradient for soft edges.
+// Spreads the cone boundary into a 3-4 tile radius gradient — no hard tile-stepped edges.
 float sample_visibility(vec2 uv) {
     vec2 t = 1.0 / map_size;
     float sum = 0.0;
@@ -49,27 +54,46 @@ void fragment() {
         float vis = sample_visibility(tex_uv);
         float explored = texture(exploration_tex, tex_uv).r;
 
-        // Don't bleed gradient into never-explored tiles
+        // Prevent gradient bleed into never-explored tiles
         if (explored < 0.01 && vis_raw < 0.01) {
             vis = 0.0;
         }
 
         if (explored < 0.01 && vis < 0.01) {
-            // Unexplored: solid near-black
+            // Unexplored: solid near-black — information zero
             COLOR = vec4(UNEXPLORED_COLOR, 1.0);
         } else {
-            // Continuous blend: clear vision (vis=1) -> light fog (vis=0).
-            // The Gaussian blur creates a smooth 3-4 tile soft gradient
-            // at the cone edge — no hard boundary.
+            // Light fog noise — fast cycle (~9s), ±0.05 breathing
+            float noise_fast = texture(noise_tex, tile * 0.03 + vec2(time * 0.11, time * 0.07)).r;
+            // Deep fog noise — slow cycle (~20s), ±0.075 breathing (more pronounced)
+            float noise_slow = texture(noise_tex, tile * 0.02 + vec2(time * 0.05, time * 0.035)).r;
 
-            // Light fog: subtle animated overlay, preserves all art/info
-            float noise_val = texture(noise_tex, tile * 0.03 + vec2(time * 0.11, time * 0.07)).r;
-            float fog_alpha = 0.28 + noise_val * 0.04;
+            // Light fog: alpha 0.25-0.35 (centered at 0.30, ±0.05 breathe)
+            // Noise remapped to [-1,+1] for symmetric breathing around baseline.
+            float light_fog_alpha = 0.30 + (noise_fast * 2.0 - 1.0) * 0.05;
 
-            // Clarity ramp from the blurred visibility
+            // Deep fog: alpha 0.55-0.70 (centered at 0.625, ±0.075 breathe)
+            float deep_fog_alpha = 0.625 + (noise_slow * 2.0 - 1.0) * 0.075;
+
+            // Blend deep <-> light fog by proximity to cone:
+            //   vis=0   (far from cone)  → deep_factor=1 → deep fog
+            //   vis=0.3 (cone gradient)  → deep_factor=0 → light fog
+            //   vis=0.85+ (inside cone)  → clarity=1     → transparent (clear)
+            float deep_factor = 1.0 - smoothstep(0.0, 0.30, vis);
+            float fog_alpha = mix(light_fog_alpha, deep_fog_alpha, deep_factor);
+
+            // Zone temperature tint (D-059/D-046/D-077):
+            // Deep fog color uses zone_tint_tex; light fog uses neutral DARK_OVERLAY.
+            // zone_tint_tex is populated per-tile from server zone_id via fog_state.gd.
+            vec3 zone_tint = texture(zone_tint_tex, tex_uv).rgb;
+
+            // Clarity ramp: transparent inside cone, fogged at edges and beyond
             float clarity = smoothstep(0.0, 0.85, vis);
             float alpha = mix(fog_alpha, 0.0, clarity);
-            vec3 color = mix(DARK_OVERLAY, vec3(0.0), clarity);
+
+            // Color: deep fog → zone temperature tint; light fog → neutral dark overlay
+            vec3 fog_color = mix(DARK_OVERLAY, zone_tint, deep_factor);
+            vec3 color = mix(fog_color, vec3(0.0), clarity);
 
             // Soft edge between explored and unexplored
             float exp_fade = smoothstep(0.0, 0.3, explored);