Add proxy_binary input to start-proxy action

[mbg]

This is useful for testing new versions of the proxy before release.

Merge / deployment checklist

• Confirm this change is backwards compatible with existing workflows.
• Confirm the readme has been updated if necessary.
• Confirm the changelog has been updated if necessary.

[Copilot]

Pull Request Overview

This PR introduces a new optional input ("proxy_binary") to the "start-proxy" action so that a custom proxy binary can be specified for testing purposes. Key changes include:

• Adding the "proxy_binary" input definition in start-proxy/action.yml.
• Updating both TypeScript and JavaScript implementations to accept the optional "proxy_binary" input.
• Wrapping process.kill calls in post-action scripts with try-catch blocks for improved error handling.

Reviewed Changes

Copilot reviewed 7 out of 7 changed files in this pull request and generated no comments.

Show a summary per file

File	Description
start-proxy/action.yml	Added the new optional "proxy_binary" input.
src/start-proxy-action.ts	Updated proxy binary determination to use the optional input if set.
src/start-proxy-action-post.ts	Added try-catch block around process.kill for better error logging.
lib/start-proxy-action.js	Updated proxy binary determination to use the optional input if set.
lib/start-proxy-action-post.js	Enhanced process.kill error handling with a try-catch block.

Comments suppressed due to low confidence (2)

src/start-proxy-action.ts:121

• Consider checking that the value returned by getOptionalInput("proxy_binary") is non-empty before defaulting to getProxyBinaryPath, as some implementations might return an empty string when no input is provided.

const proxyBin = actionsUtil.getOptionalInput("proxy_binary") ?? (await getProxyBinaryPath());

lib/start-proxy-action.js:115

• Consider verifying that the result from actionsUtil.getOptionalInput("proxy_binary") is a non-empty string before falling back to getProxyBinaryPath to ensure reliable selection of the proxy binary.

const proxyBin = actionsUtil.getOptionalInput("proxy_binary") ?? (await getProxyBinaryPath());

[aeisenberg]

What sort of error is emitted if proxy_binary doesn't exist or isn't executable? Is there a try-catch somewhere that emits a meaningful error message in this case?

[aeisenberg]

This is a question, not anything definitive. We're now giving the user an option of specifying an executable. Are there any security vulnerabilities that this opens up? Maybe the answer is "no" since this is already running in an action, which already allows execution of arbitrary code.

[mbg]

I figured we allow the same sort of thing with the tools input to the init Action, so that option is already there. Although I didn't check whether we perform any kind of validation there to verify that we were are running is safe.