Bundled CLI: split main() out of src/index.ts so the bootstrap needs no env flag; e2e project is not run by CI

[debugmcpdev]

Problem

#717 was fixed (#719) by narrowing the window in which DEBUG_MCP_SKIP_AUTO_START is set: the bundled CLI (packages/mcp-debugger/src/cli-entry.ts) sets the flag, dynamically imports src/index.js so the core's auto-start guard sees it, and restores the caller's value in finally before calling main(). That is correct today, but its correctness rests on a bundler detail — esbuild emits a lazy init_src() for the dynamic import — and nothing CI runs would catch the natural regression:

• Converting the await import('../../../src/index.js') to a static import (the file already spells typeof import('../../../src/index.js') for the type) hoists src/index.ts above the bootstrap body; the guard sees the flag unset and auto-runs main(), then bootstrap() runs entrypoint.main() again — two Commander parses, two servers on one stdin. Verified with the repo's esbuild.
• tests/integration/cli/bundled-bootstrap.test.ts runs --version, which process.exit()s inside the first main(), so its output and its env report are identical between the correct and the regressed ordering.
• The one assertion of the real behaviour, tests/e2e/mcp-server-self-debug.test.ts, lives in the e2e project, which test:ci-coverage (--project unit --project integration) and every workflow except the container job skip.

The env var is an inheritance channel by design; narrowing when it is set does not close the channel (see the sibling leak in the exit-code shim ticket).

Proposed direction

Split main() out of src/index.ts into a side-effect-free module (e.g. src/main.ts) that cli-entry.ts imports directly. Then there is no flag, no window, and isMainModule's heuristics stop being load-bearing for the bundle. Until then, keep a CI-visible guard: an integration test that starts the bundled CLI in stdio mode, sends one initialize, and asserts exactly one response frame (a double main() answers twice).

Separately worth a decision: the pre-push hook prints "full e2e runs in CI", but .github/workflows/ci.yml runs only test:ci-coverage (unit + integration) and the Docker container e2e. Either run the non-Docker e2e project in a CI job or correct the hook's message and CLAUDE.md so nobody relies on it.

Raised in the review of #719.