The last unclaimed thermal lever. Our 2026-07-24 finding: on this Plasma-Wayland
box Xwayland pins the RTX 2060 'active' regardless of runtime-PM (control=auto,
--rtd3), so the dGPU never actually suspends live and keeps drawing ~4-5 W + idle
heat. The ONLY real off is EnvyControl's 'integrated' mode (blacklist nvidia) — but
that's a persistent config change that needs a re-login, categorically unlike the
instant perf.sh modes (governor/EPP/RAPL). So it gets its own tool, not a perf-mode.

gpu-mode.sh (new, at repo root beside perf.sh)
----------------------------------------------
A guarded EnvyControl front-end: `query` (default — manager mode + live dGPU
runtime state, with the right advice per mode), `integrated` (dGPU off; warns you
lose CUDA/NVENC for demucs/audio-ML until you switch back), `hybrid` (restore with
aggressive --rtd3 3 = D3cold-when-idle). Every switch confirms (skip with -y), runs
`sudo envycontrol ...` (prompts for your password), then prints the exact re-login
step (reboot safest; verify with `./gpu-mode.sh query` + `nvidia-smi`).

Deliberately NOT added to the passwordless perf-audio sudoers whitelist: this is a
rare, considered, re-login-required switch — the web Bridge and tray must never be
able to power-cycle the GPU config unattended. Runs by hand only.

Cockpit surfacing (Bridge + tray)
---------------------------------
- perf.py: gpu_manager_mode() reads `envycontrol --query`, cached 300s (the mode is
  static within a login session; a re-login restarts this --user service and
  refreshes the cache), defensive → None if envycontrol absent. Added to snapshot()
  as `gpu_manager`.
- Bridge UI: the `gpu` chip folds it in — shows `off↻` when integrated-but-pending-
  re-login (dot green: this is the quiet goal), and in hybrid its title now names the
  manager mode and points at `./gpu-mode.sh integrated` for a real off.
- Tray tooltip mirrors it (`gpu awake·hybrid`, or `off↻` when armed).

Validation: 24 perf tests pass (2 new — parse+cache, and absent→None; snapshot-shape
now asserts dgpu/gpu_manager/thermald). Live: `./gpu-mode.sh query` reads
hybrid + active(0000:01:00.0) and fires the Xwayland warning; Bridge /api/perf serves
gpu_manager=hybrid; both services restarted clean.