feat: self-hosted socket mode entrypoint for Deno workflow apps

[vegeris]

Summary

This PR adds an entrypoint for running Deno apps via an SDK-managed socket connection

Testing

Running an app via the CLI:

• Check out this branch locally; we will point your app to the local file
• Create a new Deno app via any template (slack-public create --template https://github.com/slack-samples/deno-starter-template)
• Update the app's .slack/hooks.json file with the following:

{
  "hooks": {
    "get-hooks": "deno run -q --allow-read --allow-net https://deno.land/x/deno_slack_hooks@1.5.0/mod.ts",
    "start": "deno run -q --config=deno.jsonc --allow-read --allow-net --allow-run --allow-env --allow-sys=osRelease file:///Users/your-username/dev/deno-slack-runtime/src/self-hosted-socket-mode.ts"
  },
  "config": {
    "sdk-managed-connection-enabled": true
  }
}

• Run the app via lack run as we do for CLI-managed local apps
• The app runs normally

Running the app without the CLI:

• set the app token environment variable (export SLACK_APP_TOKEN=... and optionally, export SLACK_BOT_TOKEN=..., export SLACK_API_URL=https://dev.slack.com/api) and run the Deno command directly; deno run -q --config=deno.jsonc --allow-read --allow-net --allow-env --allow-run --allow-sys file:///Users/evegeris//dev/deno-slack-runtime/src/self-hosted-socket-mode.ts

Requirements

• I've read and understood the Contributing Guidelines and have done my best effort to follow them.
• I've read and agree to the Code of Conduct.

[vegeris]

I don't know why CLI-managed socket mode does not already require this permission to be set :not-sure:

The 'self hosted' script executes functions the same way as the 'local run' script; we run local-run-function.ts as a subprocess, which dispatches function execution to run-function.ts, which should ultimately call functions.completeSuccess or functions.completeFailure using BaseSlackAPIClient. As per Cursor: BaseSlackAPIClient uses Node’s os.release(), which in Deno is implemented with Deno.osRelease() and requires --allow-sys=osRelease

The local run start hook does run it with that permission, but the flags for the parent process don't get passed into the subprocess :confused_math_lady:
deno run -q --config=deno.jsonc --allow-read --allow-net --allow-run --allow-env --allow-sys=osRelease https://deno.land/x/deno_slack_runtime@1.1.3/local-run.ts

[vegeris]

The local run script uses the 'hook CLI protocol' for logging, but since it's not applicable here we just use the Logger that the socket mode client accepts