fix: do not echo setting values in configuration errors; test: stdio and config redaction

src/aegis_gitea_mcp/config.py

@@ -336,10 +336,11 @@ class Settings(BaseSettings):
         """Accept only granular Gitea scopes (unknown scopes make Gitea grant full access)."""
         unknown = sorted({scope for scope in value if scope not in GITEA_SCOPES})
         if unknown:
+            # The offending values are not echoed: a misplaced secret must not reach stderr.
             raise ValueError(
-                f"OAUTH_SCOPES contains unknown scope(s): {', '.join(unknown)}. "
-                "Gitea grants full access for unknown scopes, so only granular "
-                "read:/write: scopes are accepted"
+                f"OAUTH_SCOPES contains {len(unknown)} unknown scope(s). Gitea grants full "
+                "access for unknown scopes, so only granular read:/write: scopes are accepted "
+                f"({', '.join(sorted(GITEA_SCOPES))})"
             )
         if not value:
             raise ValueError("OAUTH_SCOPES must not be empty")
@@ -365,9 +366,7 @@ class Settings(BaseSettings):
         unknown = sorted({item for item in lowered if item != "all" and item not in TOOL_DOMAINS})
         if unknown:
             allowed = ", ".join(sorted(TOOL_DOMAINS | {"all"}))
-            raise ValueError(
-                f"TOOLSETS contains unknown domain(s): {', '.join(unknown)}; use {allowed}"
-            )
+            raise ValueError(f"TOOLSETS contains {len(unknown)} unknown domain(s); use {allowed}")
         if not lowered:
             raise ValueError("TOOLSETS must not be empty (use 'all')")
         return list(dict.fromkeys(lowered))