perf: cache runtime process table to stop ps spawn storm

listRuntimeProcesses spawned a full `ps -ax` on every call with no caching.
It is invoked very frequently while a team runs: runtime liveness/telemetry
snapshots are rebuilt whenever a team file changes (invalidateRuntimeSnapshotCaches
fires from ~25 sites), so the main process ended up forking ps dozens of times
per second, which is expensive from the large Electron main process and pegged
its CPU.

Add a 1s TTL cache plus in-flight coalescing on the single ps spawn point.
Liveness/telemetry callers already tolerate ~2s staleness via their own snapshot
caches and the OS process table changes negligibly within a second, so this caps
ps to <=1/s without affecting liveness correctness. Measured posix_spawn dropped
from ~146/s to ~11/s with a team running.

src/features/tmux-installer/main/infrastructure/runtime/TmuxPlatformCommandExecutor.ts

@@ -32,6 +32,25 @@ export interface RuntimeProcessTableRow {
   rssBytes?: number;
 }
 
+/**
+ * Short-lived cache window for the global process table.
+ *
+ * `listRuntimeProcesses` spawns a full `ps -ax`, which is expensive when forked
+ * from the large Electron main process. Runtime liveness/telemetry callers fire
+ * very frequently (every team file change invalidates their per-team snapshot
+ * caches), so without throttling here the main process spawns `ps` dozens of
+ * times per second while a team runs. Those callers already tolerate ~2s
+ * staleness via their own snapshot caches, and the OS process table changes
+ * negligibly within a second, so a 1s window collapses the spawn storm without
+ * affecting liveness correctness.
+ */
+const RUNTIME_PROCESS_TABLE_CACHE_TTL_MS = 1_000;
+
+interface RuntimeProcessTableCacheEntry {
+  rows: RuntimeProcessTableRow[];
+  expiresAtMs: number;
+}
+
 export function parseRuntimeProcessTable(output: string): RuntimeProcessTableRow[] {
   const rows: RuntimeProcessTableRow[] = [];
   for (const line of output.split('\n')) {
@@ -39,8 +58,13 @@ export function parseRuntimeProcessTable(output: string): RuntimeProcessTableRow
     if (enrichedMatch) {
       const pid = Number.parseInt(enrichedMatch[1], 10);
       const ppid = Number.parseInt(enrichedMatch[2], 10);
-      const cpuPercent = Number(enrichedMatch[3]);
-      const rssKb = Number(enrichedMatch[4]);
+      // `ps` formats the %cpu column with the locale decimal separator (e.g. "12,5" on
+      // de_DE/fr_FR locales, which the runtime inherits via process.env). Normalize the
+      // comma to a dot so Number() does not return NaN — otherwise the enriched parse would
+      // fail its isFinite guard and fall back to the basic parser, leaking the pcpu/rss
+      // columns into `command`.
+      const cpuPercent = Number(enrichedMatch[3]?.replace(',', '.'));
+      const rssKb = Number(enrichedMatch[4]?.replace(',', '.'));
       const command = enrichedMatch[5]?.trim() ?? '';
       if (
         Number.isFinite(pid) &&
@@ -80,6 +104,8 @@ export function parseRuntimeProcessTable(output: string): RuntimeProcessTableRow
 export class TmuxPlatformCommandExecutor {
   readonly #wslService: TmuxWslService;
   readonly #packageManagerResolver: TmuxPackageManagerResolver;
+  #runtimeProcessTableCache: RuntimeProcessTableCacheEntry | null = null;
+  #runtimeProcessTableInFlight: Promise<RuntimeProcessTableRow[]> | null = null;
 
   constructor(
     wslService = new TmuxWslService(),
@@ -192,6 +218,31 @@ export class TmuxPlatformCommandExecutor {
   }
 
   async listRuntimeProcesses(): Promise<RuntimeProcessTableRow[]> {
+    const cached = this.#runtimeProcessTableCache;
+    if (cached && cached.expiresAtMs > Date.now()) {
+      return cached.rows;
+    }
+    if (this.#runtimeProcessTableInFlight) {
+      return this.#runtimeProcessTableInFlight;
+    }
+    const request = this.#readRuntimeProcessesUncached()
+      .then((rows) => {
+        this.#runtimeProcessTableCache = {
+          rows,
+          expiresAtMs: Date.now() + RUNTIME_PROCESS_TABLE_CACHE_TTL_MS,
+        };
+        return rows;
+      })
+      .finally(() => {
+        if (this.#runtimeProcessTableInFlight === request) {
+          this.#runtimeProcessTableInFlight = null;
+        }
+      });
+    this.#runtimeProcessTableInFlight = request;
+    return request;
+  }
+
+  async #readRuntimeProcessesUncached(): Promise<RuntimeProcessTableRow[]> {
     const result =
       process.platform === 'win32'
         ? await this.#wslService.execInPreferredDistro([