COD-80 centralize terminal history/scrollback/buffer limits into config

Introduce src/config/terminal-history.ts: one place for terminal scrollback,
tmux history-limit, and PTY buffer byte caps, each overridable via env var or
the settings object and bounds-clamped via resolveTerminalHistoryConfig().
Defaults match the prior hardcoded values, so this is behavior-neutral. Wires
the resolver through buffer-limits, tmux-manager (incl. a setHistoryLimit so a
settings change applies live), session, server, system-routes, session-routes,
schemas, and the config port. Adds 4 optional settings keys (terminalScrollback
Lines, tmuxHistoryLimit, terminalBufferMaxBytes, terminalBufferTrimBytes) with
bounds + a trim<=max cross-check.

src/web/server.ts

@@ -129,6 +129,7 @@ import {
 import type { EventLoopMonitorHandle } from '../utils/index.js';
 import { MAX_CONCURRENT_SESSIONS, MAX_SSE_CLIENTS } from '../config/map-limits.js';
 import { MAX_PASTE_IMAGE_BYTES } from '../config/buffer-limits.js';
+import { resolveTerminalHistoryConfig } from '../config/terminal-history.js';
 import { SseEvent } from './sse-events.js';
 import { getLatestPlanUsage } from './plan-usage-latest.js';
 import type { ScheduledRun } from './ports/index.js';
@@ -587,6 +588,7 @@ export class WebServer extends EventEmitter {
       getGlobalNiceConfig: this.getGlobalNiceConfig.bind(this),
       getModelConfig: this.getModelConfig.bind(this),
       getClaudeModeConfig: this.getClaudeModeConfig.bind(this),
+      getTerminalHistoryConfig: this.getTerminalHistoryConfig.bind(this),
       getDefaultClaudeMdPath: this.getDefaultClaudeMdPath.bind(this),
       getLightState: this.getLightState.bind(this),
       getLightSessionsState: this.getLightSessionsState.bind(this),
@@ -1463,6 +1465,12 @@ export class WebServer extends EventEmitter {
     return {};
   }
 
+  // Resolve the bounds-clamped terminal-history config from settings.json.
+  private async getTerminalHistoryConfig() {
+    const settings = await this.readSettings();
+    return resolveTerminalHistoryConfig(settings);
+  }
+
   // Helper to get model configuration from settings
   private async getModelConfig(): Promise<{
     defaultModel?: string;