fix: expose lambda handler files via node_modules symlinks

aws-lambda-ric invokes the handler as a bare specifier —
"a9-handler-index" — and Node resolves bare names only through
node_modules. Our handler files live at /artillery/a9-handler-*.js,
unreachable that way. The previous bookworm-slim build appears to
have cached an older aws-lambda-ric whose fallback path.resolve logic
tolerated this; the DHI build pulls a newer version that doesn't.

Symlink each of the three handler files into /artillery/node_modules/.
Node follows the symlinks and uses the target's directory as
__dirname, so the relative require('./a9-handler-helpers') calls
inside the handler continue to resolve.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

Author: hassy

packages/artillery/lib/platform/aws-ecs/worker/Dockerfile

@@ -216,6 +216,16 @@ COPY --from=builder ${FUNCTION_DIR}/a9-handler-dependencies.js ${FUNCTION_DIR}/
 COPY --from=builder ${FUNCTION_DIR}/a9-handler-helpers.js ${FUNCTION_DIR}/
 COPY --from=builder ${FUNCTION_DIR}/a9-handler-index.js ${FUNCTION_DIR}/
 
+# aws-lambda-ric invokes the handler as a bare specifier ("a9-handler-index").
+# Node resolves bare names only via node_modules, so the files at /artillery/
+# aren't reachable without help. Expose each handler file inside node_modules
+# as a symlink — Node follows the symlink and treats the target dir
+# (/artillery) as __dirname, so the relative require('./a9-handler-helpers')
+# calls inside the handler still resolve.
+RUN ln -s /artillery/a9-handler-index.js        /artillery/node_modules/a9-handler-index.js \
+ && ln -s /artillery/a9-handler-helpers.js      /artillery/node_modules/a9-handler-helpers.js \
+ && ln -s /artillery/a9-handler-dependencies.js /artillery/node_modules/a9-handler-dependencies.js
+
 # Fargate worker scripts — copied from the build context (not builder stage)
 # because they may change independently of npm dependencies.
 COPY ./packages/artillery/lib/platform/aws-ecs/worker/loadgen-worker /artillery/loadgen-worker