Fix ESM import resolution: enable rewriteRelativeImportExtensions in tsconfig.json

[rowan-stein]

Problem

The docker-runner container crashes at startup with ERR_MODULE_NOT_FOUND when deployed using the standalone image (node dist/service/main.js).

Root cause: package.json declares "type": "module" (ESM), and TypeScript source files use extensionless relative imports (e.g., import './config'). The tsc compiler does not rewrite import specifiers, so the compiled JS files contain import './config' instead of import './config.js'. Node.js ESM requires explicit .js extensions and crashes immediately.

The old platform monorepo worked because it used tsx (a TypeScript runtime that handles resolution transparently) instead of node dist/....

Fix

Add "rewriteRelativeImportExtensions": true to tsconfig.json compilerOptions. This is a TypeScript 5.7+ feature that rewrites ./foo → ./foo.js in the compiled output. The repo already uses TypeScript ^5.8.3.

Verification

After the fix:

pnpm build
head -5 dist/service/main.js
# Should show: import './env.js'; import { loadRunnerConfig } from './config.js'; etc.

Also verify pnpm lint, pnpm build, and pnpm test still pass.

Context

Discovered during bootstrap CI (agynio/bootstrap_v2 PR #97) — docker-runner pod enters CrashLoopBackOff when deployed with chart 0.1.1.