Add cmux <path> to open directories and Homebrew binary stanza (#705)

* Add `cmux <path>` to open directories and Homebrew binary stanza

CLI: `cmux .` or `cmux /path/to/dir` opens a new workspace at the
given directory. If the app isn't running, it launches first and waits
for the socket. Also adds `--cwd` flag to `new-workspace`.

Server: `workspace.create` now accepts an optional `cwd` parameter,
passed through to `TabManager.addWorkspace(workingDirectory:)`.

Homebrew: adds `binary` stanza to the cask so `cmux` CLI is globally
available after `brew install --cask cmux`. Updated both the cask file,
the CI workflow template, and the manual release script so automated
version bumps preserve the stanza.

* Address review: validate cwd type, fix socket detection, propagate errors

- looksLikePath now also matches paths containing `/` (e.g. `foo/bar`)
- openPath uses socket connection attempt instead of fileExists to detect
  whether the app is running (Unix sockets may not appear on filesystem)
- launchApp/activateApp now throw instead of swallowing errors with try?
- Server validates that cwd param is a string, returns invalid_params error
  if wrong type is passed

scripts/build-sign-upload.sh

@@ -177,6 +177,7 @@ cask "cmux" do
   depends_on macos: ">= :ventura"
 
   app "cmux.app"
+  binary "#{appdir}/cmux.app/Contents/Resources/bin/cmux"
 
   zap trash: [
     "~/Library/Application Support/cmux",