feat: GPU process list with per-process VRAM/utilization and kill

Add a GPU process table to the Performance tab showing which processes
use the selected GPU, with per-process VRAM, GPU utilization, CPU, host
memory, and command. Includes a kill endpoint (SIGTERM/SIGKILL, with
optional parent kill) behind a confirm dialog.

- nvcurve/hal/processes.py: NVML + /proc process enumeration
- server.py: GET /api/processes, POST /api/processes/kill (refuses to
  signal init/kthreadd)
- frontend: ProcessList component, API client, types
- tests: test_processes.py
- docs: API reference for the new endpoints

frontend/src/api/client.ts

@@ -8,6 +8,7 @@ import type {
   FanState,
   FanPoint,
   DashboardInfo,
+  ProcessListResponse,
 } from "../types.js";
 
 export class ApiError extends Error {
@@ -119,6 +120,17 @@ export const api = {
   voltage: (gpuIndex: number) =>
     get<{ voltage_uv: number; voltage_mv: number }>("/voltage", gpuIndex),
   monitor: (gpuIndex: number) => get<MonitoringSample>("/monitor", gpuIndex),
+  processes: (gpuIndex: number) =>
+    get<ProcessListResponse>("/processes", gpuIndex),
+  killProcess: (
+    pid: number,
+    signal: "TERM" | "KILL" = "TERM",
+    parent = false,
+  ) =>
+    post<{ ok: boolean; pid: number; signal: string; parent: boolean }>(
+      "/processes/kill",
+      { pid, signal, parent },
+    ),
   snapshots: (gpuIndex: number) => get<SnapshotInfo[]>("/snapshots", gpuIndex),
 
   /** Write per-point frequency deltas. deltas: { pointIndex: deltaKhz } */