docs(browser): add CDP recovery boundaries

Author: MagMueller

packages/bcode-browser/skills/browser-execute/SKILL.md

@@ -104,6 +104,8 @@ const page = targets.find(t => t.type === "page" && !t.url.startsWith("chrome://
 await session.use(page.targetId)
 ```
 
+If a target-scoped command throws `CdpError` code `-32001` (`Session with given id not found`), the browser connection is still usable but the target session is stale. List targets again, `session.use(...)` the intended page, and retry the rejected command once. Repeated `session.connect()` calls do not replace a stale target session.
+
 ## Driving a page
 Domain methods follow `session.<Domain>.<method>(params)` and return Promises. 
 The full surface (652 commands) is the Chrome DevTools Protocol.
@@ -142,6 +144,8 @@ await session.Page.captureScreenshot({ format: "png" })
 // for the rare case you want to process it programmatically.
 ```
 
+`Page.navigate` can return a non-empty `errorText` instead of throwing. Treat it as a failed navigation. If `ERR_TUNNEL_CONNECTION_FAILED` persists, reloading, reattaching, or reconnecting to the same endpoint cannot change its proxy route; use another source or replace the cloud browser instead of retrying it.
+
 ## Reusing code
 The agent-workspace is per-project: `./.bcode/agent-workspace/`. 
 Use this to write memory files, scripts, and helper functions.