chore: drop docs/-walk shim in _find_m_standard()

[rafael5]

Summary

Follow-up to m-standard PR #6 which relocated docs/integrated/ → integrated/. The ("", "docs") walk in _find_m_standard() was a compatibility shim for the layout-shift window; with that window closed, it's dead code on any fresh m-standard checkout.

Three-line simplification:

-    for repo in repo_candidates:
-        for sub in ("", "docs"):
-            cand = repo / sub if sub else repo
-            if (cand / "integrated").exists():
-                return cand
+    for repo in repo_candidates:
+        if (repo / "integrated").exists():
+            return repo

Plus docstring trimmed of the layout-shift rationale.

Test plan

• keyword + doctor + LSP symbol tests green locally (46 passed)
• CI green on this PR