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/sodium-options.json

@@ -0,0 +1,30 @@
+{
+  "quality": {
+    "weather_quality": "DEFAULT",
+    "leaves_quality": "DEFAULT",
+    "enable_vignette": true,
+    "use_closest_point_entity_sort": false
+  },
+  "advanced": {
+    "enable_memory_tracing": false,
+    "use_advanced_staging_buffers": true,
+    "cpu_render_ahead_limit": 3
+  },
+  "performance": {
+    "chunk_builder_threads": 0,
+    "chunk_build_defer_mode": "ALWAYS",
+    "animate_only_visible_textures": true,
+    "use_entity_culling": true,
+    "use_fog_occlusion": true,
+    "use_block_face_culling": true,
+    "use_no_error_g_l_context": true,
+    "quad_splitting_mode": "SAFE"
+  },
+  "notifications": {
+    "has_cleared_donation_button": false,
+    "has_seen_donation_prompt": false
+  },
+  "debug": {
+    "terrain_sorting_enabled": true
+  }
+}