docs(skills): require bundled llms index

Author: chenjiahan

.agents/skills/rstack-cli-best-practices/SKILL.md

@@ -14,10 +14,7 @@ installed documentation is the source of truth for the project's Rstack version.
 1. Start with `node_modules/rstack/dist/docs/llms.txt`, then read only the linked pages relevant to
    the task before proposing or making changes.
 
-2. If `llms.txt` is unavailable, start with `node_modules/rstack/dist/docs/index.md` and search the
-   documentation directory with `rg -n "<keyword>" node_modules/rstack/dist/docs`.
-
-3. For exact CLI flags and behavior, also run `rs -h` or `rs <command> -h` when supported.
+2. For exact CLI flags and behavior, also run `rs -h` or `rs <command> -h` when supported.
 
 If the bundled docs are not available at that path, locate the installed `rstack` package. If they
 are still unavailable, verify that `rstack` is installed, report the installed version, and use CLI