perf: harden runtime for weaker hardware

docs/BUILD_IN_PUBLIC_PLAN.md

@@ -419,6 +419,18 @@ grass, conifers, richer deciduous silhouettes, and oversized butterflies add
 life without changing simulation authority. The matched review lives in
 [`baselines/JAJCE_CENTER_02.md`](baselines/JAJCE_CENTER_02.md).
 
+The world now also has a structural weak-PC contract. High restores that
+authored look; Balanced is the runtime default at 85% 3D scale with ordinary
+fog, shorter two-split shadows, roughly half the grass, fewer interactors, and
+no volumetric fog; Low uses 70% 3D scale, one short shadow region, disables
+glow/volumetric fog/color adjustment, and stops grass rendering and processing.
+Use `-- --quality=high|balanced|low` for reproducible runs. Headless regression
+proves the profiles are reversible, presentation-only, resource-isolated, and
+warning-clean under Compatibility feature selection. This does not exercise a
+real OpenGL GPU because headless Godot uses its dummy renderer. A representative
+weak-PC High/Low capture with CPU/GPU p50/p95, memory, and draw statistics is
+still required before claiming the visual frame-time exit condition.
+
 ### Exit condition
 
 The lookdev scene can produce a compelling 10–20 second clip with no gameplay.
@@ -854,6 +866,15 @@ Completed:
 49. `Jajce Seasons 16`: a deterministic four-day seasonal cycle halves gather
     yields and pauses berry regrowth on the cold day, so the garden keeps
     producing real scarcity the player can help address.
+50. Runtime health and weak-PC pass: the default Balanced presentation tier
+    removes volumetric fog, halves grass density, lowers 3D scale, and shortens
+    shadows; Low stops grass and costly effects while High remains reversible.
+    UI/environment probes are rate-limited, failed creature paths back off,
+    player resource prompts use the loaded-anchor grid, and simulation/combat
+    ID callbacks use disposable indexes. Combat authority now enforces range,
+    faction, unscaled player cooldown, recovery, melee approach, death ordering,
+    and real pantry plunder. Benchmark workload v2 validates one combatant per synthetic
+    NPC and records 90.63 ticks/s at 600 records with stable checksums.
 
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