perf(startup): lazy-import SSE/HTTP transport stacks in CLI actions

[debugmcpdev]

Fixes #400

stdio mode — every claude mcp add config — statically imported all three transport command modules, dragging express and the SDK's streamableHttp/sse/express stacks (body-parser, qs, send, …) into the module graph of a server that never uses them.

Change

• src/index.ts: the SSE and HTTP command modules are now imported with await import() inside their commander action closures, so they only load when that subcommand actually runs (same pattern as check-rust-binary). The stdio command module stays static — it has no HTTP dependencies and is the default path.
• The handleSSECommand/handleHttpCommand re-exports from index.ts are dropped. No consumers existed: tests and tooling import the command modules directly.
• src/cli/stdio-command.ts: StdioOptions becomes an import type (it's a type-only use).

Laziness is locked in by a test

tests/unit/index-lazy-imports.test.ts mocks express with a factory that flips a flag on evaluation, imports the entry point, and asserts the flag stayed false. Before this change the test fails (express evaluates on import); after, it passes. vi.mock intercepts dynamic imports too, so the existing index.test.ts handler-closure assertions keep working unchanged.

Measured (mem-bench, this machine, Windows)

node scripts/mem-bench.mjs --target dist --scenario idle — median RSS at after-initialize, 5 trials:

	RSS med	peak med
main (2014358c)	108.5 MB	108.5 MB
this branch	97.4 MB	97.5 MB

−11.1 MB (−10.2%) idle stdio footprint.

Note: in the docker/npx single-file bundles the bytes still ship, but the express module graph is no longer parsed/executed on stdio startup — the win is parse/execute + heap, as scoped in the issue.

Verification

• Full npm test green (259 files / 3947 tests), npm run lint clean
• tests/unit/index.test.ts + tests/unit/cli/* pass unchanged

🤖 Generated with Claude Code

[codecov]

Codecov Report

❌ Patch coverage is 66.66667% with 2 lines in your changes missing coverage. Please review.

Files with missing lines	Patch %	Lines
src/index.ts	66.66%	2 Missing ⚠️

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