docs: add v0.1.5 release notes

docs/release-notes/v0.1.5.md

@@ -0,0 +1,21 @@
+# tdc v0.1.5
+
+This release makes TiDB Cloud Starter cluster creation shorter and more deterministic for users, scripts, and agents. Because tdc currently manages Starter clusters exclusively, `tdc db create-db-cluster` now defaults the cluster type to `starter`; users only need to provide the cluster name and can still explicitly pass `--db-cluster-type starter` when desired.
+
+```bash
+export CLUSTER_ID="$(tdc db create-db-cluster \
+  --db-cluster-name agent-db \
+  --wait \
+  --query id \
+  --output text)"
+```
+
+Unsupported explicit cluster types continue to fail before a request is sent. The release also refines command help descriptions and Preview labels across the Filesystem command surface, and simplifies the README quick-start, configuration, mount, and help workflows.
+
+Upgrade an existing installation with:
+
+```bash
+tdc update --check
+tdc update
+tdc --version
+```