… into bazel

Since Bazel was completely stripped out of the repository, the
generator-tests.yaml workflow was failing because it attempted
to strip GCC flags from .bazelrc and run bazelisk commands.

This commit updates the CI workflow to:
- Use standard 'npm run compile' and 'npm test' instead of bazelisk.
- Reference the built protoc-plugin.js path directly instead of bazel-bin.
- Manually zip the generated .test-out directories instead of relying
  on Bazel's testlogs.

… into bazel

When running tests locally or in CI without Bazel, the generated
TypeScript entry point (gapic-generator-typescript.js) was losing
its executable permissions, causing baseline tests to fail with
'Permission denied'.

This commit explicitly invokes the generator with 'node' in the
test utility to ensure cross-platform execution without relying
on file permissions.

When Bazel was removed, the build step stopped copying the
'templates/' directory to the 'build/' output folder. This
caused the generator to fail with ENOENT errors when it
tried to locate the Nunjucks templates during code generation.

This commit updates the 'npm run compile' script to explicitly
copy the templates directory into 'build/' after tsc finishes.

With Bazel removed, the gapic-generator-typescript no longer has
a local, managed version of the `protoc` binary injected via the
environment variable.

When it attempts to find `protoc` in the local file system using
`fs.existsSync('protoc')`, it fails and throws an error. This commit
updates the check to skip `fs.existsSync` if the resolved path is
just the string 'protoc', allowing the generator to correctly defer
to the system PATH where protoc is already installed in CI.

With Bazel removed, the gapic-generator-typescript no longer has
a local, managed version of the `protoc` binary. The
generator-tests.yaml workflow was failing because it attempted
to spawn `protoc` without it being installed in the container
environment.

This commit updates the CI workflow to download and install
protoc v25.3 globally before running the tests.

The gapic-generator-typescript expects the 'PROTOC_PATH' environment
variable to point to the protoc binary, or it falls back to looking
for 'protoc' in the system PATH.

This commit updates generator-tests.yaml to explicitly provide the
PROTOC_PATH environment variable to 'npm test' pointing to the newly
installed /usr/local/bin/protoc binary, ensuring the tests don't
fail with ENOENT when trying to spawn protoc.

When Bazel was removed, the protoc-plugin.js file generated by
tsc no longer had executable permissions. When protoc attempted
to invoke it via the --plugin flag, it failed with 'program not
found or is not executable'.

This commit updates the fallback logic in gapic-generator-typescript.ts
to prepend 'node ' to the protoc plugin path, ensuring protoc
executes it correctly using the Node.js runtime without relying
on file permissions.

The gapic-error-conformance binary invoked the protoc-plugin.js
directly, which failed because the generated script no longer has
executable permissions after the removal of Bazel.

This updates the CI workflow to execute the plugin via the Node.js
runtime ('node ...') instead of relying on chmod and the file's
shebang.

When protoc invokes a plugin via the --plugin=name=path flag,
it expects 'path' to be an actual executable binary/script.
Prepending 'node' to the path caused protoc to fail to find
the executable.

This commit updates gapic-generator-typescript to explicitly
run fs.chmodSync(pluginPath, 0o755) before passing the path
to protoc, ensuring the generated script is executable and
can use its node shebang.

When protoc compiles proto files that use the experimental
Editions feature (like google/showcase/v1beta1/testing.proto),
it throws a fatal error unless the --experimental_editions flag
is explicitly passed.

This commit updates the generator to always pass this flag to protoc,
ensuring it doesn't crash when encountering these newer proto files
now that we are relying on the system protoc (v25+).

The gapic-error-conformance tool expects an executable binary or
script for the -plugin flag and fails with 'no such file or directory'
when passed a string like 'node file.js'.

This commit reverts the workflow to use chmod +x on the generated
plugin script so it can be passed directly to the conformance tool,
since we previously updated the typescript code to ensure the script
itself is generated with execution permissions.