Fix CI race condition on self-hosted runner (#19)

* Fix zsh ZDOTDIR wrapper + log parsing with -- messages

* Fix CI race condition: serialize self-hosted builds with concurrency group

Two workflows racing on the same self-hosted runner caused DerivedData
corruption (release's rm -rf nuked DerivedData while CI was building).
Add shared concurrency group and scope DerivedData cleanup to project.

.github/workflows/ci.yml

@@ -9,6 +9,9 @@ on:
 jobs:
   ui-tests:
     runs-on: self-hosted
+    concurrency:
+      group: self-hosted-build
+      cancel-in-progress: false
     steps:
       - name: Checkout
         uses: actions/checkout@v4

.github/workflows/release.yml

@@ -12,6 +12,9 @@ permissions:
 jobs:
   build-sign-notarize:
     runs-on: self-hosted
+    concurrency:
+      group: self-hosted-build
+      cancel-in-progress: false
     steps:
       - name: Checkout
         uses: actions/checkout@v4
@@ -53,7 +56,7 @@ jobs:
       - name: Clear SPM cache
         run: |
           rm -rf ~/Library/Caches/org.swift.swiftpm
-          rm -rf ~/Library/Developer/Xcode/DerivedData
+          rm -rf ~/Library/Developer/Xcode/DerivedData/GhosttyTabs-*
 
       - name: Configure SwiftPM cache
         run: |