docs(readme,strings): YAML seed-only semantics documented — interactive flow, duplicate guards, no implicit entry changes on block removal (t30 U1)

README.md

@@ -92,6 +92,28 @@ the inter-digit **delay** (0.05–1.0 s, default 0.1) and the optional
 behavior). Both are consumed by `play_media` with
 `media_content_type: channel`.
 
+### YAML seeding (optional, seed-only)
+
+An optional `nvidia_shield:` block in `configuration.yaml` **seeds** an
+interactive setup flow — nothing is created without the user walking the
+standard flow, and pairing stays interactive exactly as with UI setup:
+
+```yaml
+nvidia_shield:
+  - name: Living Room
+    adb_host: 10.0.0.31      # or protocol_host for the PIN-pairing hint
+    adb_port: 5555
+```
+
+`protocol_host` is a prefill hint only (the PIN pairing still happens in
+the flow). Blocks without protocol/adb hosts are ignored with a warning.
+Duplicate guards: a block matching an existing entry's host (or its
+virtual `yaml:…` unique_id) aborts and never re-seeds a UI-configured
+host. Removing the YAML block creates or deletes nothing — entries live
+in the storage registry and require user consent to remove. Deleting/re-
+adding is the only way to move an imported entry between hosts; the UI is
+the contractual path (YAML is the seed, the flow is the truth).
+
 ### Raw `adb_command` service (opt-in)
 
 When enabled in the integration's options (`adb_command_enabled`, **default