feat(coding-agent): improved Python startup performance with prelude caching and shared gateway mode

- Added Python prelude caching to improve startup performance by caching helper functions and module discovery results.
- Added OMP_DEBUG_STARTUP environment variable for detailed startup stage tracing across initialization pipeline.
- Changed Python kernel initialization to require shared gateway mode, removing support for local kernel gateway startup.
- Improved error handling in shared gateway acquisition with automatic retries on 5xx status codes.
- Added repro-stuck.ts script for reproducing and debugging rare CLI hang issues with Chrome DevTools integration.
- Added trace-loader.ts preload script for tracing module resolution during startup diagnostics.

packages/coding-agent/src/capability/index.ts

@@ -8,6 +8,12 @@
  */
 import * as os from "node:os";
 import * as path from "node:path";
+
+/** Conditional startup debug prints (stderr) when OMP_DEBUG_STARTUP is set */
+const debugStartup = process.env.OMP_DEBUG_STARTUP
+	? (stage: string) => process.stderr.write(`[startup] ${stage}\n`)
+	: () => {};
+
 import type { Settings } from "../config/settings";
 import { clearCache as clearFsCache, cacheStats as fsCacheStats, invalidate as invalidateFs } from "./fs";
 import type {
@@ -109,9 +115,12 @@ async function loadImpl<T>(
 	const results = await Promise.all(
 		providers.map(async provider => {
 			try {
+				debugStartup(`capability:${capability.id}:${provider.id}:start`);
 				const result = await provider.load(ctx);
+				debugStartup(`capability:${capability.id}:${provider.id}:done`);
 				return { provider, result };
 			} catch (error) {
+				debugStartup(`capability:${capability.id}:${provider.id}:error`);
 				return { provider, error };
 			}
 		}),