feat(help): fall back to remote docs for unanswerable questions

help.md now names https://docs.bmad-method.org/llms.txt as the place to
look when it and the installed skills cannot answer a BMad question; the
index also names the source repository as the final authority. The hub
skill's constraints direct that fetch before conceding a limitation,
restoring the remote-docs grounding the CSV-era bmad-help had via its
_meta row.

skills/bmad/SKILL.md

@@ -78,8 +78,10 @@ If something could not be read, say so and do not guess.
 - Use a configured communication language when it is already available from
   current context or a permitted read-only configuration read. Otherwise answer
   in the user's language. Never run the resolver merely to obtain a language.
-- If the allowed sources cannot support a general BMad question, state that
-  limitation instead of inventing an answer or using a forbidden source.
+- If the allowed sources cannot support a general BMad question, fetch the
+  remote documentation named in `references/help.md` and answer from it. If
+  that too cannot answer, state the limitation instead of inventing an answer
+  or using a forbidden source.
 
 ## Answer Shape
 

skills/bmad/references/help.md

@@ -134,6 +134,13 @@ A run is complete when the intent is satisfied, its chosen checks pass, and
 no chosen review leaves material unresolved findings — not when every skill
 has been traversed.
 
+## When this document is not enough
+
+For a BMad question this document and the installed skills cannot answer,
+fetch `https://docs.bmad-method.org/llms.txt` and follow the links relevant
+to the question. It indexes the full documentation site and names the source
+repository, which is the final authority on how anything actually behaves.
+
 ## Where things land
 
 Durable specs and their story lists live under `{output_folder}/specs`;