docs: client-perf analysis, bench harness and work journal

Everything the next agent needs to run the Phase 2 optimisation loop on a
machine that can launch the client:

- analysis/client-perf/: LEVERS (ranked levers + corrections), BENCH-MATRIX
  (world, scenes, config IDs, blocks B0-B14 with decision rules),
  PLAYER-TUNING, SPAWN-TUNING, research briefs, the jar scanner and its
  output, observed default configs, and proposed-configs/ (build.py
  generates tiers and bench variants and fails on unknown keys;
  apply_variant.py applies a variant and merges options.txt).
- analysis/client-perf/bench/onion-bench/: bench-world datapack (scene
  teleports, Create grid, mob pen, sound storm, 120 s teleport tour).
- analysis/audit/: the static recipe/dependency audit, including gen_fixes.py,
  which generates the shipped Paxi datapack and was never tracked.
- phase0/: per-machine measurement harness (Steam Deck, 7700K/1060,
  6700K/1080 Ti).
- .pi/journal.md: running work log; read it first.

All of it is packwizignored, so nothing here ships to players.

analysis/client-perf/data/observed-default-configs/entity_model_features.json

@@ -0,0 +1,36 @@
+{
+  "allowedCEM": "ALL",
+  "logModelCreationData": false,
+  "debugOnRightClick": false,
+  "renderModeChoice": "NORMAL",
+  "vanillaModelHologramRenderMode_2": "OFF",
+  "modelExportMode": "NONE",
+  "automaticModelExporting": false,
+  "attemptPhysicsModPatch_2": "CUSTOM",
+  "modelUpdateFrequency": "Average",
+  "entityRenderModeOverrides": {},
+  "entityPhysicsModPatchOverrides": {},
+  "entityVanillaHologramOverrides": {},
+  "modelsNamesDisabled": [],
+  "allowEBEModConfigModify": true,
+  "animationLODDistance": 20,
+  "retainDetailOnLowFps": true,
+  "retainDetailOnLargerMobs": true,
+  "animationFrameSkipDuringIrisShadowPass": true,
+  "preventFirstPersonHandAnimating": false,
+  "onlyClientPlayerModel": false,
+  "doubleChestAnimFix": true,
+  "enforceOptifineVariationRequiresDefaultModel": false,
+  "enforceOptifineVariationRequiresDefaultModel_v2": false,
+  "resetPlayerModelEachRender": true,
+  "resetPlayerModelEachRender_v2": true,
+  "onlyDebugRenderOnHover": false,
+  "enforceOptifineSubFoldersVariantOnly": false,
+  "enforceOptiFineAnimSyntaxLimits": true,
+  "allowOptifineFallbackProperties": true,
+  "showReloadErrorToast": true,
+  "exportRotations": false,
+  "asmMaths": true,
+  "logASM": false,
+  "parrotShoulderPositionAnimatesByDefault": true
+}