chore(bench): add client bench harness and Phase 2 handoff

The client now boots cleanly on the bench machine (the CAC spawn-key
crash was fixed in 8e8483d). Add the harness used to drive bench scenes
and capture frametimes, the bench-world generation workflow, and a
self-contained handoff brief. All files live under analysis/ (packwizignored),
so nothing player-facing changes.

- harness/rcon.py: minimal RCON client for the temp worldgen server
- harness/run_scene.py: apply variant -> launch Prism under MangoHud ->
  xdotool scene commands -> p50/p95/p99/1%-low from the CSV
- HANDOFF.md: state, gotchas, next steps
- build.py: disable DH autoUpdater for bench variants (suppress modal)

analysis/client-perf/notes-serverlog-triage.md

@@ -0,0 +1,60 @@
+# Triage: /home/logan/onion-mc/logs/latest.log (dedicated server)
+
+7165 lines, 986,551 bytes. **Covers mid-session only**: starts `14Oct2026 00:00:29` with
+RCON keepalive lines (server was already running); no mod-loading/startup phase is in
+this file. Ends ~19:50. NOTE: log timestamps say 2026 — quoted as-is.
+
+## 1) Missing dependency / missing mod / "Mod file ... requires" errors
+**no hits.** Searched (case-insensitive): `missing (mod|dependency)`, `Mod file .* requires`,
+`mandatory`, `dependency`, `requires` — 0 matches in the whole file.
+
+## 2) Mixin apply failures / fatal crashes
+**no hits.** 0 lines containing `mixin` at all; 0 `/FATAL]` lines; no `Critical injection
+failure`, `crash report`, `Exception`, `Segfault`, or `Failed to apply`. Server ran
+continuously (periodic Sable sub-level saves every ~5 min) with no crash.
+
+## 3) "fishermans" / biome-modifier parse errors or warnings
+**no hits.** 0 matches for `fisher` (any case) and 0 for `biome` — so no biome-modifier
+parse errors/warnings either.
+
+## 4) ftbteams / dev/ftb/mods/ftbteams
+**no hits** for `ftbteams` (any case). `ftb` case-insensitively matches 15 lines, **all**
+from `dev.ftb.mods.ftbbackups.Backups` (routine FTB Backups runs at 12:28, 14:28, 16:28),
+e.g. line 4465:
+```
+4465:[14Oct2026 12:28:03.472] [Server thread/INFO] [dev.ftb.mods.ftbbackups.Backups/]: backup starting: Server
+```
+No errors or references to ftbteams jar paths.
+
+## 5) YACL "Failed to deserialize" (fowlplay / crittersandcompanions)
+**no hits.** 0 lines contain `yacl`, 0 contain `Failed to deserialize`, 0 mention
+`fowlplay` or `crittersandcompanions`.
+
+## 6) Startup-complete marker / "Done (N.NNNs)!"
+**Absent from this file.** No `Done (`, `Starting minecraft server`, `Preparing level`,
+or startup banner — the file begins mid-run (`[14Oct2026 00:00:29.211] ... Thread RCON
+Client /127.0.0.1 started`, line 1). Startup output is in an earlier rotated log
+(e.g. `logs/2026-10-1*.log.gz`). The server was up throughout; line 68 shows a LAN
+connection attempt refused by whitelist:
+```
+68:[14Oct2026 00:12:07.186] [Server thread/INFO] [net.minecraft.server.network.ServerLoginPacketListenerImpl/]: Disconnecting FishNet (/127.0.0.1:51840): You are not white-listed on this server!
+```
+
+## 7) Error/fatal counts + sample
+- Literal `[ERROR]`: **0** — this log's format is `[Server thread/ERROR]`; counting `/ERROR]` gives **8 lines**.
+- `[FATAL]` / `/FATAL]`: **0**. `[WARN]`: **0**.
+- All 8 ERROR lines collapse to 4 distinct messages (each twice), all benign
+  `ServerRecipeBook` noise at 12:28:02 (right before the 12:28:03 backup), lines 4450–4457:
+```
+4450:[14Oct2026 12:28:02.967] [Server thread/ERROR] [net.minecraft.stats.ServerRecipeBook/]: Tried to load unrecognized recipe: etched:radio removed now.
+4451:[14Oct2026 12:28:02.968] [Server thread/ERROR] [net.minecraft.stats.ServerRecipeBook/]: Tried to load unrecognized recipe: etched:music_label removed now.
+4452:[14Oct2026 12:28:02.968] [Server thread/ERROR] [net.minecraft.stats.ServerRecipeBook/]: Tried to load unrecognized recipe: etched:boombox removed now.
+4453:[14Oct2026 12:28:02.968] [Server thread/ERROR] [net.minecraft.stats.ServerRecipeBook/]: Tried to load unrecognized recipe: etched:blank_music_disc removed now.
+```
+
+## Bottom line
+No evidence here of missing-mods, mixin failures, fishermans/biome-modifier parse issues,
+ftbteams references, or YACL deserialize problems — and no crash. If client-side symptom
+reports stem from startup-time mod loading, the signal will be in the **rotated startup
+log** or the **client** log, not this mid-session server `latest.log`. No files were
+modified; no processes touched.