chore(ci): run lint, test, and docs on pull requests

Rename ci-main.yml to ci.yml and add a pull_request trigger so PRs
targeting main get the same lint/test/docs signal as post-merge runs.
Job names are unchanged so existing required-status-check rules keep
working.

Author: m3nu

.github/workflows/ci-main.yml .github/workflows/ci.yml.github/workflows/ci-main.yml renamed to .github/workflows/ci.yml

@@ -1,16 +1,19 @@
-name: ci-main
+name: ci
 
 on:
   push:
     branches:
       - main
+  pull_request:
+    branches:
+      - main
   workflow_dispatch:
 
 permissions:
   contents: read
 
 concurrency:
-  group: ci-main-${{ github.ref }}
+  group: ci-${{ github.ref }}
   cancel-in-progress: true
 
 jobs: