fix: restore package-type Image branching (regression in v1.1.1)

[JamBalaya56562]

Summary

Fixes #70.

v1.1.1 broke package-type: Image deployments. The action now fails for
every Image user with:

Packaging code artifacts from
##[error]Failed to package artifacts: Code artifacts directory path must be provided
##[error]Action failed with error: Code artifacts directory path must be provided

The output Packaging code artifacts from is the smoking gun — the
trailing space shows that code-artifacts-dir is empty (as expected for
Image deploys), yet packageCodeArtifacts() is being called anyway.

Root cause

The durable-functions refactor in #65 removed the package-type
branching from index.js. v1.1.0 had:

if (packageType === 'Zip') {
  finalZipPath = await packageCodeArtifacts(codeArtifactsDir);
} else if (packageType === 'Image') {
  core.info(`Using container image: ${imageUri}`);
}

v1.1.1 collapsed that to:

core.info(`Packaging code artifacts from ${codeArtifactsDir}`);
let finalZipPath = await packageCodeArtifacts(codeArtifactsDir);

The same regression hit createFunction (Code: { ImageUri },
PackageType: 'Image', the Runtime/Handler/Layers/ImageConfig gates,
and the Cannot change package type of existing Lambda function guard
were all deleted) and updateFunctionCode (the ImageUri branch was
removed).

Fix

Restores the v1.1.0 package-type gating across run(),
createFunction, updateFunctionConfiguration,
hasConfigurationChanged, and updateFunctionCode. The durable-
functions feature added in #65 (durableConfig, parsedDurableConfig,
DurableConfig) is preserved unchanged — both features now coexist.

Why the regression slipped through

The existing test suite mocks createFunction and updateFunctionCode
in most tests rather than exercising the real implementations, and
container_image_support.test.js only covered validations.js — there
was no test that drove the real index.js flow with
package-type: Image. This PR adds two regression tests that call the
real createFunction and updateFunctionCode with
package-type: Image and assert:

• ImageUri is sent and ZipFile is not
• PackageType: 'Image' is set
• Runtime / Handler / Layers are omitted for Image

dist

dist/index.js is rebuilt with npm run build (ncc 0.36.1).

Test plan

• npx jest __tests__/container_image_support.test.js — 7/7 pass (5 existing + 2 new regression tests)
• Full npx jest — 232 pass; 11 pre-existing path-resolution failures in validations.test.js are POSIX-vs-Windows artifacts unrelated to this change
• Manual deploy of an Image-type Lambda using the example workflow to confirm the original error no longer occurs