test: add Lambda deploy plan coverage

[op-simoneromeo]

Summary

• changes deploy-lambda build to write an inspectable lambda-deploy.json plan instead of probing AWS credentials during build
• keeps dry-run shipping side-effect free and delays the live AWS function lookup until real ship mode
• adds Lambda config coverage for region, environment, layers, memory, timeout, publish, and mocked AWS CLI update/create paths

Validation

• corepack pnpm@9.12.0 exec vitest run packages/targets/deploy-lambda/src/index.test.ts
• corepack pnpm@9.12.0 --filter @profullstack/sh1pt-target-deploy-lambda typecheck
• corepack pnpm@9.12.0 --filter @profullstack/sh1pt-target-deploy-lambda build
• git diff --check

Refs #6