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/flywheel-client.toml

@@ -0,0 +1,14 @@
+#Select the backend to use. Set to "DEFAULT" to let Flywheel decide.
+backend = "DEFAULT"
+#Enable or disable instance update limiting with distance.
+limitUpdates = true
+#The number of worker threads to use. Set to -1 to let Flywheel decide. Set to 0 to disable parallelism. Requires a game restart to take effect.
+# Default: -1
+# Range: -1 ~ 4
+workerThreads = -1
+
+#Config options for Flywheel's built-in backends.
+[flw_backends]
+	#How smooth Flywheel's shader-based lighting should be. May have a large performance impact.
+	#Allowed Values: FLAT, TRI_LINEAR, SMOOTH, SMOOTH_INNER_FACE_CORRECTED
+	lightSmoothness = "SMOOTH"