docs: document package KV cache effects

packages/bash/bash/README.md

@@ -37,6 +37,8 @@ The seam also owns the per-session mode override vocabulary: the log-only `'bash
 
 Indirectly, through `dsh-tool-bash`, which turns executor output and sandbox facts into guidance and retained tool-result tokens.
 
+**KV Cache effect**: No direct invalidation; the named consumer owns any request-prefix changes.
+
 ## Known Limitations and Deferred Work
 
 - **No interactive-input vocabulary** — `stdin` is written once at spawn and closed; the seam has no channel to feed a running task and no PTY session concept.