fix(session): preserve history across storage relocation

Co-authored-by: lmzopq <1646888+lmzopq@users.noreply.github.com>

docs/cli-reference.md

@@ -94,6 +94,24 @@ follow the printed WebUI **Settings → Models** or `nanobot onboard --wizard` r
 | `nanobot agent --no-markdown` | Print plain text instead of Rich-rendered Markdown |
 | `nanobot agent --logs` | Show runtime logs while chatting |
 
+## Session Storage and Rollback
+
+Session JSONL files live under `<config-dir>/sessions/<workspace-id>/`, outside the
+agent-readable workspace. On the first upgraded start, nanobot safely migrates existing
+`<workspace>/sessions/*.jsonl` files after verifying an atomic copy. Stop every old nanobot
+process that uses the workspace before upgrading; old and new binaries must not write the
+same session concurrently.
+
+To prepare a downgrade, stop nanobot and copy the current sessions back to the path understood
+by older releases:
+
+```bash
+nanobot sessions restore-workspace --config ./bot-a/config.json --workspace ./bot-a/workspace
+```
+
+The command never deletes the external store and refuses to overwrite a different existing
+workspace file. Back up both the config directory and workspace before changing versions.
+
 In interactive mode, `Enter` sends the current message. Press `Alt+Enter` to add a newline before sending.
 
 Interactive mode exits with `exit`, `quit`, `/exit`, `/quit`, `:q`, or `Ctrl+D`.