adds skill for handling upstream changes and merging to local

plugins/compound-engineering/skills/upstream-merge/assets/merge-triage-template.md

@@ -0,0 +1,57 @@
+---
+status: pending
+priority: p2
+issue_id: "XXX"
+tags: [upstream-merge]
+dependencies: []
+---
+
+# Merge Conflict: [filename]
+
+## File Info
+
+| Field | Value |
+|-------|-------|
+| **File** | `path/to/file` |
+| **Category** | agent / command / skill / config / other |
+| **Conflict Type** | content / modify-delete / add-add |
+
+## What Changed
+
+### Remote Version
+
+[What the upstream version added, changed, or intended]
+
+### Local Version
+
+[What the local version added, changed, or intended]
+
+## Diff
+
+<details>
+<summary>Show diff</summary>
+
+```diff
+[Relevant diff content]
+```
+
+</details>
+
+## Recommendation
+
+**Suggested resolution:** Accept remote / Keep local / Merge both / Keep deleted
+
+[Reasoning for the recommendation, considering the local fork's guiding principles]
+
+## Decision
+
+**Resolution:** *(filled during triage)*
+
+**Details:** *(specific merge instructions if "merge both")*
+
+## Acceptance Criteria
+
+- [ ] Resolution applied correctly
+- [ ] No content lost unintentionally
+- [ ] Local intent preserved
+- [ ] File validates (JSON/YAML if applicable)