chore: fix missing node_modules in lambda zip v2

[ava-silver]

What does this PR do?

Fixes the macro Lambda zip missing node_modules/ (issue #242). Two changes:

1. Inlines the install step into build. yarn berry does NOT auto-run arbitrary pre/post hooks (only well-known lifecycle scripts like prepare, postinstall). PR [SVLS-8827] upgrade to yarn berry and add npm minimal age gate #238's yarn berry migration silently broke the postbuild hook so the install step never ran in any environment. New build script: tsc && cp package.json dist/package.json && npm install --omit=dev --prefix dist.

2. Replaces the false-positive CI check with one that actually inspects the zip. The previous check (cd dist && node -e "require('./src/index.js')") always passed because Node's module resolution walked up from dist/ into serverless/node_modules/ (populated by yarn install) and found loglevel there — even when dist/node_modules/ was empty. The new check zips dist/, extracts to a clean /tmp/ directory (no parent node_modules/ to fall back to), and runs the require there.

Motivation

v0.27.1 still ships a broken Lambda. PR #244 changed the postbuild script and added a "verify Lambda bundle" step that both passed CI and shipped — but neither actually did anything: the postbuild was dead code under yarn berry, and the verify step was finding deps in the parent's node_modules. See #242 and the ZD ticket for customer reports.

Testing Guidelines

• cd serverless && rm -rf dist && yarn build → confirm dist/node_modules/loglevel and dist/node_modules/@aws-sdk/ exist
• Zip + extract + require sanity check (what the new CI step does):

  cd serverless/dist && zip -q -r /tmp/test.zip ./
  rm -rf /tmp/verify && mkdir /tmp/verify && unzip -q /tmp/test.zip -d /tmp/verify
  cd /tmp/verify && node -e "require('./src/index.js')"
  

Proof

CI:

• Failing run on commit fb3308a (install step stripped) — Cannot find module 'loglevel' from extracted zip, exact production error.
• Passing run on the current commit.

End-to-end against real AWS + Datadog (US1, sandbox account 425362996713):

• Built the fixed zip locally → 9.1 MB / 4274 files (vs. broken 128 KB / 148 files in v0.27.1).
• Uploaded to S3 and deployed the macro stack ava-silver-macro-fix242 in us-east-1 — no Cannot find module 'loglevel' failure on the macro Lambda's cold start (this is the regression we fixed).
• Deployed a sample SAM stack ava-fix242-hello-stack with Transform: DatadogServerless. The macro instrumented the function as expected: Datadog-Node22 layer v132 + Datadog-Extension layer v92, handler rewritten to /opt/nodejs/node_modules/datadog-lambda-js/handler.handler, all DD_* env vars set.
• Invoked ava-fix242-hello 20+ times. Lambda logs show the extension running cleanly and successfully flushing traces: DD_EXTENSION | DEBUG | Request succeeded status=202 Accepted for https://trace.agent.datadoghq.com/api/v0.2/traces.
• Datadog APM: traces for service:ava-fix242-test env:sandbox (last 1h). Sample trace IDs you can plug into https://ddserverless.datadoghq.com/apm/trace/<id> (US1 org corresponding to the API key used): 4986331605483463556, 6788063569943029167, 8662992718378330393.

Types of changes

• Bug fix

Check all that apply

• This PR's description is comprehensive

[ava-silver]

• chore: fix missing node_modules in lambda zip v2 #248 👈 (View in Graphite)
• main

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[codecov-commenter]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 82.72%. Comparing base (49cd234) to head (b780b52).

Additional details and impacted files

@@           Coverage Diff           @@
##             main     #248   +/-   ##
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  Coverage   82.72%   82.72%           
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  Files          19       19           
  Lines         938      938           
  Branches      231      231           
=======================================
  Hits          776      776           
  Misses         91       91           
  Partials       71       71           

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