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/config/buffer-limits.ts

@@ -9,11 +9,13 @@
  * - Terminal buffer: 2MB max × 20 = 40MB worst case
  * - Text output: 1MB max × 20 = 20MB worst case
  * - Messages: ~1KB each × 1000 × 20 = 20MB worst case
- * - Total buffer overhead: ~80MB (acceptable for long-running server)
+ * - Total buffer overhead: ~80MB (acceptable for a long-running server)
  *
  * @module config/buffer-limits
  */
 
+import { DEFAULT_TERMINAL_BUFFER_MAX_BYTES, DEFAULT_TERMINAL_BUFFER_TRIM_BYTES } from './terminal-history.js';
+
 // ============================================================================
 // Terminal Buffer Limits
 // ============================================================================
@@ -21,17 +23,17 @@
 /**
  * Maximum terminal buffer size in characters.
  * Contains raw terminal output with ANSI escape sequences.
- * Reduced from 5MB to 2MB for better render performance.
+ * Sourced from terminal-history config (env/settings overridable).
  * Override: CODEMAN_MAX_TERMINAL_BUFFER (bytes)
  */
-export const MAX_TERMINAL_BUFFER_SIZE = parseInt(process.env.CODEMAN_MAX_TERMINAL_BUFFER || '') || 2 * 1024 * 1024;
+export const MAX_TERMINAL_BUFFER_SIZE = DEFAULT_TERMINAL_BUFFER_MAX_BYTES;
 
 /**
  * Size to trim terminal buffer to when max is exceeded.
  * Keeps the most recent portion to preserve context.
  * Override: CODEMAN_TRIM_TERMINAL_TO (bytes)
  */
-export const TRIM_TERMINAL_TO = parseInt(process.env.CODEMAN_TRIM_TERMINAL_TO || '') || 1.5 * 1024 * 1024;
+export const TRIM_TERMINAL_TO = DEFAULT_TERMINAL_BUFFER_TRIM_BYTES;
 
 // ============================================================================
 // Text Output Buffer Limits

src/config/terminal-history.ts

@@ -0,0 +1,65 @@
+/**
+ * Defaults, bounds, and resolution for terminal history retention.
+ *
+ * Centralizes the terminal scrollback, tmux history-limit, and server PTY buffer
+ * byte caps that were previously scattered as hardcoded literals. Each value is
+ * overridable (env var or the settings object) and clamped to a sane range via
+ * resolveTerminalHistoryConfig(). Defaults intentionally match the prior
+ * hardcoded values, so introducing this module is behavior-neutral.
+ */
+
+export const DEFAULT_TERMINAL_SCROLLBACK_LINES = 50_000;
+export const DEFAULT_TMUX_HISTORY_LIMIT = 50_000;
+export const DEFAULT_TERMINAL_BUFFER_MAX_BYTES =
+  parseInt(process.env.CODEMAN_MAX_TERMINAL_BUFFER || '', 10) || 2 * 1024 * 1024;
+export const DEFAULT_TERMINAL_BUFFER_TRIM_BYTES =
+  parseInt(process.env.CODEMAN_TRIM_TERMINAL_TO || '', 10) || 1.5 * 1024 * 1024;
+
+export const MIN_TERMINAL_SCROLLBACK_LINES = 1_000;
+export const MAX_TERMINAL_SCROLLBACK_LINES = 1_000_000;
+export const MIN_TERMINAL_BUFFER_BYTES = 1024 * 1024;
+export const MAX_TERMINAL_BUFFER_BYTES = 128 * 1024 * 1024;
+
+export interface TerminalHistoryConfig {
+  terminalScrollbackLines: number;
+  tmuxHistoryLimit: number;
+  terminalBufferMaxBytes: number;
+  terminalBufferTrimBytes: number;
+}
+
+function boundedInt(value: unknown, fallback: number, min: number, max: number): number {
+  if (typeof value !== 'number' || !Number.isFinite(value)) return fallback;
+  return Math.max(min, Math.min(max, Math.trunc(value)));
+}
+
+export function resolveTerminalHistoryConfig(settings: Record<string, unknown> = {}): TerminalHistoryConfig {
+  const terminalBufferMaxBytes = boundedInt(
+    settings.terminalBufferMaxBytes,
+    DEFAULT_TERMINAL_BUFFER_MAX_BYTES,
+    MIN_TERMINAL_BUFFER_BYTES,
+    MAX_TERMINAL_BUFFER_BYTES
+  );
+  const terminalBufferTrimBytes = boundedInt(
+    settings.terminalBufferTrimBytes,
+    Math.min(DEFAULT_TERMINAL_BUFFER_TRIM_BYTES, terminalBufferMaxBytes),
+    MIN_TERMINAL_BUFFER_BYTES,
+    terminalBufferMaxBytes
+  );
+
+  return {
+    terminalScrollbackLines: boundedInt(
+      settings.terminalScrollbackLines,
+      DEFAULT_TERMINAL_SCROLLBACK_LINES,
+      MIN_TERMINAL_SCROLLBACK_LINES,
+      MAX_TERMINAL_SCROLLBACK_LINES
+    ),
+    tmuxHistoryLimit: boundedInt(
+      settings.tmuxHistoryLimit,
+      DEFAULT_TMUX_HISTORY_LIMIT,
+      MIN_TERMINAL_SCROLLBACK_LINES,
+      MAX_TERMINAL_SCROLLBACK_LINES
+    ),
+    terminalBufferMaxBytes,
+    terminalBufferTrimBytes,
+  };
+}