fix(ci): run PR automation via pull_request_target for fork PRs

.github/workflows/auto-author-assign.yaml

@@ -1,7 +1,11 @@
 ---
 name: "Auto Author Assign"
+# Uses pull_request_target so the assign step gets a read-write token on fork
+# PRs (pull_request hands forks a read-only token, which makes the assignees
+# API call fail). Safe here: the workflow never checks out or executes PR-head
+# code, it only assigns the author via the API from the event payload.
 on:
-  pull_request:
+  pull_request_target:
     types: [opened, reopened, synchronize]
 permissions:
   contents: read

.github/workflows/mark-ready-when-ready.yml

@@ -1,7 +1,13 @@
 name: Mark PR Ready When Ready
 
+# Uses pull_request_target so the mark-ready step gets a read-write token on
+# fork PRs (pull_request hands forks a read-only token, so contents: write is
+# denied and the job fails). Safe here: the workflow never checks out or
+# executes PR-head code. The action reads the PR number, draft flag, labels,
+# and head SHA from the event payload and acts only via the API, so running in
+# the base-repo context does not evaluate any untrusted code.
 on:
-  pull_request:
+  pull_request_target:
     types: [opened, edited, labeled, unlabeled, synchronize]
 
 permissions: