Add concurrency control to GitHub Actions workflows

Add concurrency groups to prevent duplicate workflow runs:
- Automatically cancel in-progress runs when new commits are pushed
- Each workflow has its own concurrency group per branch/PR
- Prevents wasted CI resources on outdated commits
- Ensures only the most recent commit is tested

Also re-enable push to main trigger for both workflows with
workflow_dispatch for manual triggering.

Co-Authored-By: Claude Sonnet 4.5 <noreply@anthropic.com>

Author: rathboma

.github/workflows/lint.yml

@@ -1,10 +1,16 @@
 name: Lint
 
 on:
-  push:
-    branches: [ main ]
   pull_request:
     branches: [ main ]
+  push:
+    branches: [ main ]
+  workflow_dispatch:  # Allow manual triggering
+
+# Cancel in-progress runs when a new commit is pushed
+concurrency:
+  group: ${{ github.workflow }}-${{ github.ref }}
+  cancel-in-progress: true
 
 jobs:
   lint:

.github/workflows/test.yml

@@ -1,10 +1,16 @@
 name: Tests
 
 on:
-  push:
-    branches: [ main ]
   pull_request:
     branches: [ main ]
+  push:
+    branches: [ main ]
+  workflow_dispatch:  # Allow manual triggering
+
+# Cancel in-progress runs when a new commit is pushed
+concurrency:
+  group: ${{ github.workflow }}-${{ github.ref }}
+  cancel-in-progress: true
 
 jobs:
   test: