Release v1.23.0 (#31)

* Rename cmuxterm to cmux across entire codebase

- Rename GitHub repos: manaflow-ai/cmuxterm -> manaflow-ai/cmux,
  manaflow-ai/homebrew-cmuxterm -> manaflow-ai/homebrew-cmux
- Rename bundle IDs: com.cmuxterm.app -> com.cmux.app
- Rename CLI: CLI/cmuxterm.swift -> CLI/cmux.swift
- Rename homebrew submodule: homebrew-cmuxterm -> homebrew-cmux
- Update all socket paths: /tmp/cmuxterm*.sock -> /tmp/cmux*.sock
- Update all GitHub URLs, DMG names, Sparkle URLs
- Update all source files, scripts, tests, docs, CI workflows

* Bump version to 1.23.0

Sources/Update/UpdateTestSupport.swift

@@ -61,13 +61,13 @@ enum UpdateTestSupport {
 
     private static func makeAppcastItem(displayVersion: String) -> SUAppcastItem? {
         let enclosure: [String: Any] = [
-            "url": "https://example.com/cmuxterm.zip",
+            "url": "https://example.com/cmux.zip",
             "length": "1024",
             "sparkle:version": displayVersion,
             "sparkle:shortVersionString": displayVersion,
         ]
         let dict: [String: Any] = [
-            "title": "cmuxterm \(displayVersion)",
+            "title": "cmux \(displayVersion)",
             "enclosure": enclosure,
         ]
         return SUAppcastItem(dictionary: dict)