fix: remove cpulimit, use nice only for CPU priority

cpulimit -f interfered with Claude's Ink terminal UI causing duplicate
prompt rendering. Replaced with nice-only approach.

- Remove cpulimit entirely (was causing display issues)
- Rename CpuLimitConfig -> NiceConfig for clean naming
- Simplify wrapWithCpuLimit -> wrapWithNice
- Update UI labels and settings key (cpuLimit -> nice)

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

src/screen-manager.ts

@@ -19,7 +19,7 @@ import { spawn, execSync } from 'node:child_process';
 import { existsSync, readFileSync, mkdirSync, writeFile } from 'node:fs';
 import { dirname, join } from 'node:path';
 import { homedir } from 'node:os';
-import { ScreenSession, ProcessStats, ScreenSessionWithStats, PersistedRespawnConfig, getErrorMessage, CpuLimitConfig, DEFAULT_CPU_LIMIT_CONFIG } from './types.js';
+import { ScreenSession, ProcessStats, ScreenSessionWithStats, PersistedRespawnConfig, getErrorMessage, NiceConfig, DEFAULT_NICE_CONFIG } from './types.js';
 
 // ============================================================================
 // Claude CLI PATH Resolution
@@ -56,68 +56,13 @@ const DEFAULT_STATS_INTERVAL_MS = 2000;
 /** Maximum retry attempts for carriage return (3) */
 const CR_MAX_ATTEMPTS = 3;
 
-/** Cached result for cpulimit availability check */
-let _cpulimitAvailable: boolean | null = null;
-
 /**
- * Checks if cpulimit is available on the system.
- * Result is cached after the first check.
- *
- * @returns true if cpulimit is installed and accessible
+ * Wraps a command with `nice` for priority adjustment.
  */
-export function cpulimitAvailable(): boolean {
-  if (_cpulimitAvailable !== null) return _cpulimitAvailable;
-
-  try {
-    execSync('which cpulimit', { encoding: 'utf-8', timeout: EXEC_TIMEOUT_MS });
-    _cpulimitAvailable = true;
-  } catch {
-    _cpulimitAvailable = false;
-  }
-
-  return _cpulimitAvailable;
-}
-
-/**
- * Wraps a command with CPU limiting options.
- *
- * Uses `nice` to set process priority and optionally `cpulimit` for
- * hard CPU usage limits (if installed).
- *
- * @param cmd - The command to wrap
- * @param config - CPU limit configuration
- * @returns The wrapped command string
- *
- * @example
- * ```typescript
- * // With cpulimit installed:
- * wrapWithCpuLimit('claude --dangerously-skip-permissions', { enabled: true, niceValue: 10, cpuLimitPercent: 80 })
- * // Returns: 'cpulimit -l 80 -f -- nice -n 10 claude --dangerously-skip-permissions'
- *
- * // Without cpulimit:
- * wrapWithCpuLimit('claude --dangerously-skip-permissions', { enabled: true, niceValue: 10, cpuLimitPercent: 80 })
- * // Returns: 'nice -n 10 claude --dangerously-skip-permissions'
- * ```
- */
-export function wrapWithCpuLimit(cmd: string, config: CpuLimitConfig): string {
+export function wrapWithNice(cmd: string, config: NiceConfig): string {
   if (!config.enabled) return cmd;
-
-  // Clamp nice value to valid range (-20 to 19)
   const niceValue = Math.max(-20, Math.min(19, config.niceValue));
-
-  // Clamp CPU limit to valid range (1-100)
-  const cpuLimit = Math.max(1, Math.min(100, config.cpuLimitPercent));
-
-  // Always apply nice for priority reduction
-  let wrappedCmd = `nice -n ${niceValue} ${cmd}`;
-
-  // Add cpulimit if available and requested
-  if (config.useCpulimitIfAvailable && cpulimitAvailable()) {
-    // -l: limit percentage, -f: follow forked processes
-    wrappedCmd = `cpulimit -l ${cpuLimit} -f -- ${wrappedCmd}`;
-  }
-
-  return wrappedCmd;
+  return `nice -n ${niceValue} ${cmd}`;
 }
 
 
@@ -292,11 +237,9 @@ export class ScreenManager extends EventEmitter {
    * @param workingDir - Working directory for the screen session
    * @param mode - 'claude' for Claude CLI or 'shell' for bash
    * @param name - Optional display name for the session
-   * @param cpuLimitConfig - Optional CPU limiting configuration
-   * @returns The created screen session metadata
-   * @throws {Error} If screen creation fails
+   * @param niceConfig - Optional nice priority configuration
    */
-  async createScreen(sessionId: string, workingDir: string, mode: 'claude' | 'shell', name?: string, cpuLimitConfig?: CpuLimitConfig): Promise<ScreenSession> {
+  async createScreen(sessionId: string, workingDir: string, mode: 'claude' | 'shell', name?: string, niceConfig?: NiceConfig): Promise<ScreenSession> {
     const screenName = `claudeman-${sessionId.slice(0, 8)}`;
 
     // Security: Validate screenName and workingDir to prevent command injection
@@ -313,9 +256,8 @@ export class ScreenManager extends EventEmitter {
     const claudeDir = findClaudeDir();
     const pathExport = claudeDir ? `export PATH="${claudeDir}:$PATH" && ` : '';
 
-    // Environment variables must be exported, not passed inline to nice/cpulimit
-    // Using inline VAR=value before cpulimit/nice doesn't work because they try to
-    // execute VAR=value as a command
+    // Environment variables must be exported, not passed inline to nice
+    // Using inline VAR=value before nice doesn't work correctly
     const envExports = [
       'export CLAUDEMAN_SCREEN=1',
       `export CLAUDEMAN_SESSION_ID=${sessionId}`,
@@ -328,9 +270,9 @@ export class ScreenManager extends EventEmitter {
       ? 'claude --dangerously-skip-permissions'
       : '$SHELL';
 
-    // Apply CPU limiting if configured
-    const cpuConfig = cpuLimitConfig || DEFAULT_CPU_LIMIT_CONFIG;
-    const cmd = wrapWithCpuLimit(baseCmd, cpuConfig);
+    // Apply nice priority if configured
+    const config = niceConfig || DEFAULT_NICE_CONFIG;
+    const cmd = wrapWithNice(baseCmd, config);
 
     try {
       // Start screen in detached mode
@@ -815,11 +757,6 @@ export class ScreenManager extends EventEmitter {
     }
   }
 
-  // Check if cpulimit is available on the system (for hard CPU limiting)
-  static isCpulimitAvailable(): boolean {
-    return cpulimitAvailable();
-  }
-
   // Send input directly to screen session using screen -X stuff
   // This bypasses the attached PTY and sends input directly to the screen
   sendInput(sessionId: string, input: string): boolean {