ci: add upstream-ledger-sync daily action (#164)

Add upstream-ledger-sync action to run daily to pull upstream commits, update triage.jsonl, and open a PR against dev so the list can be automatically updated to stay in line with upstream.

.github/workflows/upstream-ledger-sync.yml

@@ -0,0 +1,48 @@
+name: Upstream Ledger Sync
+
+on:
+  schedule:
+    - cron: "17 12 * * *" # daily ~08:17 ET
+  workflow_dispatch:
+
+concurrency:
+  group: upstream-ledger-sync
+  cancel-in-progress: false
+
+permissions:
+  contents: write
+  pull-requests: write
+
+jobs:
+  sync:
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v7
+        with:
+          ref: dev
+          fetch-depth: 0
+
+      - name: Add upstream remote
+        run: |
+          git remote add upstream https://github.com/langchain-ai/open-swe.git || true
+
+      - uses: actions/setup-python@v5
+        with:
+          python-version: "3.12"
+
+      - name: Sync ledger
+        run: python3 scripts/triage.py sync
+
+      - name: Open/refresh PR if the ledger changed
+        uses: peter-evans/create-pull-request@v7
+        with:
+          base: dev
+          branch: bot/upstream-ledger-sync
+          commit-message: "chore: sync upstream triage ledger"
+          title: "chore: sync upstream triage ledger"
+          body: |
+            Automated 'scripts/triage.py sync'. New rows land as **Untriaged** - triage each (adopt/defer/won't-merge) before merging.
+          labels: upstream-sync
+          add-paths: |
+            docs/upstream-sync/triage.jsonl
+            docs/upstream-sync/triage.md