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.

test/terminal-history-schema.test.ts

@@ -0,0 +1,67 @@
+import { describe, it, expect } from 'vitest';
+import { SettingsUpdateSchema } from '../src/web/schemas.js';
+import {
+  MAX_TERMINAL_SCROLLBACK_LINES,
+  MIN_TERMINAL_SCROLLBACK_LINES,
+  MAX_TERMINAL_BUFFER_BYTES,
+  MIN_TERMINAL_BUFFER_BYTES,
+} from '../src/config/terminal-history.js';
+
+describe('SettingsUpdateSchema — terminal history keys', () => {
+  it('accepts valid in-range terminal-history settings', () => {
+    const res = SettingsUpdateSchema.safeParse({
+      terminalScrollbackLines: 100_000,
+      tmuxHistoryLimit: 100_000,
+      terminalBufferMaxBytes: 32 * 1024 * 1024,
+      terminalBufferTrimBytes: 24 * 1024 * 1024,
+    });
+    expect(res.success).toBe(true);
+  });
+
+  it('accepts a settings object that omits the terminal-history keys', () => {
+    const res = SettingsUpdateSchema.safeParse({ allowedTools: 'Bash' });
+    expect(res.success).toBe(true);
+  });
+
+  it('rejects scrollback below the minimum', () => {
+    const res = SettingsUpdateSchema.safeParse({ terminalScrollbackLines: MIN_TERMINAL_SCROLLBACK_LINES - 1 });
+    expect(res.success).toBe(false);
+  });
+
+  it('rejects scrollback above the maximum', () => {
+    const res = SettingsUpdateSchema.safeParse({ tmuxHistoryLimit: MAX_TERMINAL_SCROLLBACK_LINES + 1 });
+    expect(res.success).toBe(false);
+  });
+
+  it('rejects buffer bytes outside the byte bounds', () => {
+    expect(SettingsUpdateSchema.safeParse({ terminalBufferMaxBytes: MIN_TERMINAL_BUFFER_BYTES - 1 }).success).toBe(
+      false
+    );
+    expect(SettingsUpdateSchema.safeParse({ terminalBufferMaxBytes: MAX_TERMINAL_BUFFER_BYTES + 1 }).success).toBe(
+      false
+    );
+  });
+
+  it('rejects non-integer values', () => {
+    expect(SettingsUpdateSchema.safeParse({ terminalScrollbackLines: 12_345.5 }).success).toBe(false);
+  });
+
+  it('rejects trim > max via the cross-field superRefine', () => {
+    const res = SettingsUpdateSchema.safeParse({
+      terminalBufferMaxBytes: 4 * 1024 * 1024,
+      terminalBufferTrimBytes: 8 * 1024 * 1024,
+    });
+    expect(res.success).toBe(false);
+    if (!res.success) {
+      expect(res.error.issues.some((i) => i.path.includes('terminalBufferTrimBytes'))).toBe(true);
+    }
+  });
+
+  it('allows trim == max', () => {
+    const res = SettingsUpdateSchema.safeParse({
+      terminalBufferMaxBytes: 8 * 1024 * 1024,
+      terminalBufferTrimBytes: 8 * 1024 * 1024,
+    });
+    expect(res.success).toBe(true);
+  });
+});