Problem: the laptop ran hot even idle, and the bafd3133 RAPL watt caps were
committed but NEVER deployed — the live /usr/local/sbin/perf-audio predated
them, so every --cool set clock-% while RAPL sat at the BIOS 135W (measured
90C under an all-core encode). Watts are the thermal lever, not percent.

- perf.sh: new --silent ("smart-silent") — powersave + EPP power + 55% clock
  ceiling + a hard 12W/25W RAPL cap + allow_dgpu_suspend (nudge the discrete
  GPU toward D3cold) + audio still RT. Quieter than --cool without disabling
  turbo (low PL2 keeps SuperDirt DSP transients from xrunning). Tunable via
  SILENT_PL1_W / SILENT_MAX_PCT.
- perf-audio.sudoers: whitelist --silent (flag-scoped, no wildcard).
- tools/bridge/perf.py: MODES gains silent (tray + web inherit it);
  detect_mode disambiguates silent vs cool by EPP; snapshot() gains cores_pct
  (per-cpu util deltas), dgpu (runtime_status), thermald, watts (live RAPL
  caps), power_w (actual draw — null until energy_uj is unlocked, then lights).
- ui/index.html: the bar is a cockpit now — 16 "dancing cores" (height=util,
  colour=temp, hover=cpu/util/temp), folded chips (watt cap / dGPU asleep-awake
  / thermald), a distinct teal+snowflake tint for Silent, and a 60s temp+power
  sparkline.
- perf-tray.py: the icon's decorative sine is now a REAL temp-history
  sparkline; tooltip + menu fold in cap/gpu/thermald.

Verified: POST /api/perf {silent} -> live RAPL 12/25W; {cool} -> 28/50W; the
135W furnace is leashed. perf tests 7-pass.