docs(git): add body length example with ❌/✅ pair

.ai/instructions/skills/git.instructions.md

@@ -100,6 +100,32 @@ Types: `feat`, `fix`, `docs`, `refactor`, `chore`
   - ✅ `disable redis sub-chart`
   - ✅ `set queue type to level`
 
+**Body length example — what "too much explanation" looks like vs. the correct version:**
+
+❌ Too long — describes runtime behavior, not the change:
+```text
+chore(minio): pin image to RELEASE.2025-10-15T17-29-55Z
+
+Chart 5.4.0 bundles RELEASE.2024-12-18 which does not return Last-Modified
+metadata on objects. Thanos compactor falls back to ULID creation time and
+deletes valid blocks as stale partial uploads (>48h old).
+
+Also add comment on thanos-sidecar image noting all Thanos containers
+(compactor, blocks-exporter, init container, ghost cleanup job) share
+this single image reference.
+```
+
+✅ Correct — states what changed, one line of context for the why:
+```text
+chore(minio): pin image to RELEASE.2025-10-15T17-29-55Z
+
+RELEASE.2024-12-18 (Chart 5.4.0) lacks Last-Modified on objects; compactor
+deletes valid blocks as stale partial uploads.
+
+Add comment on thanos-sidecar: image is shared by compactor, blocks-exporter,
+init container and ghost cleanup job.
+```
+
 **All projects:**
 - Treat commit messages as change logs of repository state, not behavior reports
 - Never include runtime status, deployment outcomes, test run narratives, or manual operation confirmations unless the user explicitly asks for a release note or status report instead of a commit message