feat: add issue assignee workflow (#21003)

Signed-off-by: Kartik Angiras <angiraskartik@gmail.com>

docs/issue-and-pr-automation.md

@@ -113,7 +113,45 @@ process.
     ensure every issue is eventually categorized, even if the initial triage
     fails.
 
-### 5. Release automation
+### 5. Automatic unassignment of inactive contributors: `Unassign Inactive Issue Assignees`
+
+To keep the list of open `help wanted` issues accessible to all contributors,
+this workflow automatically removes **external contributors** who have not
+opened a linked pull request within **7 days** of being assigned. Maintainers,
+org members, and repo collaborators with write access or above are always exempt
+and will never be auto-unassigned.
+
+- **Workflow File**: `.github/workflows/unassign-inactive-assignees.yml`
+- **When it runs**: Every day at 09:00 UTC, and can be triggered manually with
+  an optional `dry_run` mode.
+- **What it does**:
+  1. Finds every open issue labeled `help wanted` that has at least one
+     assignee.
+  2. Identifies privileged users (team members, repo collaborators with write+
+     access, maintainers) and skips them entirely.
+  3. For each remaining (external) assignee it reads the issue's timeline to
+     determine:
+     - The exact date they were assigned (using `assigned` timeline events).
+     - Whether they have opened a PR that is already linked/cross-referenced to
+       the issue.
+  4. Each cross-referenced PR is fetched to verify it is **ready for review**:
+     open and non-draft, or already merged. Draft PRs do not count.
+  5. If an assignee has been assigned for **more than 7 days** and no qualifying
+     PR is found, they are automatically unassigned and a comment is posted
+     explaining the reason and how to re-claim the issue.
+  6. Assignees who have a non-draft, open or merged PR linked to the issue are
+     **never** unassigned by this workflow.
+- **What you should do**:
+  - **Open a real PR, not a draft**: Within 7 days of being assigned, open a PR
+    that is ready for review and include `Fixes #<issue-number>` in the
+    description. Draft PRs do not satisfy the requirement and will not prevent
+    auto-unassignment.
+  - **Re-assign if unassigned by mistake**: Comment `/assign` on the issue to
+    assign yourself again.
+  - **Unassign yourself** if you can no longer work on the issue by commenting
+    `/unassign`, so other contributors can pick it up right away.
+
+### 6. Release automation
 
 This workflow handles the process of packaging and publishing new versions of
 the Gemini CLI.