chore: remove dead code and unused exports (-159 lines)

Remove confirmed-unused code found via team-based codebase analysis:
- Dead interfaces: SessionResponse (types.ts), PlannerResult (plan-orchestrator.ts)
- Dead functions: withTimeout (session.ts), getOpenCodeAugmentedPath, resetOpenCodeCache (opencode-cli-resolver.ts)
- Dead config constants: MAX_RUN_SUMMARY_EVENTS, TRIM_RUN_SUMMARY_TO, MAX_MESSAGES_PER_CHANNEL (buffer-limits.ts), MAX_TRACKED_AGENTS, MAX_SUBAGENT_ACTIVITY_PER_AGENT, MAX_TOOL_RESULTS_PER_AGENT, COMPLETED_TODO_TTL_MS (map-limits.ts)
- Dead legacy code: idleTimer property + clearIdleTimer() no-op method + 6 call sites (respawn-controller.ts)
- Stale barrel re-exports: createAnsiPatternFull/Simple, validateTokenCounts/Cost, stripAnsi, normalizePhrase, getOpenCodeAugmentedPath (utils/index.ts)
- Un-exported internal-only symbols: ErrorMessages (types.ts), destroyRalphLoop (ralph-loop.ts)

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

src/session.ts

@@ -49,7 +49,6 @@ import {
 
 export type { BackgroundTask } from './task-tracker.js';
 export type { RalphTrackerState, RalphTodoItem, ActiveBashTool } from './types.js';
-export { withTimeout };
 
 /** Line buffer flush interval (100ms) - forces processing of partial lines */
 const LINE_BUFFER_FLUSH_INTERVAL = 100;
@@ -97,29 +96,6 @@ const NEWLINE_SPLIT_PATTERN = /\r?\n/;
 // Claude CLI PATH resolution — shared utility
 import { getAugmentedPath } from './utils/claude-cli-resolver.js';
 
-/**
- * Wraps a promise with a timeout to prevent indefinite hangs.
- * If the promise doesn't resolve within the timeout, rejects with TimeoutError.
- *
- * @param promise - The promise to wrap
- * @param timeoutMs - Timeout in milliseconds
- * @param operation - Description of the operation for error messages
- * @returns Promise that resolves/rejects with the original result or timeout error
- */
-function withTimeout<T>(promise: Promise<T>, timeoutMs: number, operation: string): Promise<T> {
-  let timeoutId: NodeJS.Timeout;
-
-  const timeoutPromise = new Promise<never>((_, reject) => {
-    timeoutId = setTimeout(() => {
-      reject(new Error(`${operation} timed out after ${timeoutMs}ms`));
-    }, timeoutMs);
-  });
-
-  return Promise.race([promise, timeoutPromise]).finally(() => {
-    clearTimeout(timeoutId);
-  });
-}
-
 /**
  * Represents a JSON message from Claude CLI's stream-json output format.
  * Messages are newline-delimited JSON objects parsed from PTY output.