Purge standalone OAuth setup for Gmail and Gcal

- Deleted gmail_oauth_setup.py and gcal_oauth_setup.py (Skald handles OAuth)
- Removed google-auth-oauthlib dependency from requirements.txt and connector.json
- Simplified setup_instructions to point to Skald's OAuth flow
- Updated docstrings and error messages in *_mcp_server.py (no more refs to
  *_oauth_setup.py, point to Skald OAuth / env-var instead)
- connectors.json: removed oauth_setup.py from files[], updated sha256 hashes

connectors/gmail/gmail_mcp_server.py

@@ -17,7 +17,6 @@ Provides read, modify, and send access to Gmail via the Gmail API v1.
 
 Skald mode: Skald injects credentials via GMAIL_CREDS_JSON env var (authorized_user JSON).
 Standalone mode: reads from GMAIL_CREDS_PATH or ./secrets/gmail_creds.json.
-Run scripts/gmail_oauth_setup.py first to generate the OAuth token (standalone).
 """
 
 from __future__ import annotations
@@ -308,21 +307,20 @@ def _format_google_error(e: Exception, api_label: str) -> str:
     if RefreshError is not None and isinstance(e, RefreshError):
         return (
             f"Error: {api_label} API token refresh failed (the refresh token may have been revoked "
-            "or expired). Re-run scripts/gmail_oauth_setup.py to re-authenticate."
+            "or expired). Re-authenticate via Skald's OAuth flow (Sign in from the connector page)."
         )
 
     if HttpError is not None and isinstance(e, HttpError):
         status = getattr(e, "status_code", None)
         if status == 401:
             return (
-                f"Error: {api_label} API rejected the access token (401). The OAuth token is invalid "
-                "or revoked. Re-run scripts/gmail_oauth_setup.py to re-authenticate."
-            )
+            f"Error: {api_label} API rejected the access token (401). The OAuth token is invalid "
+            "or revoked. Re-authenticate via Skald's OAuth flow (Sign in from the connector page)."            )
         if status == 403:
             return (
                 f"Error: {api_label} API returned 403 Forbidden. The OAuth scopes granted are "
                 "insufficient for this operation, or the Gmail API is disabled in the Google Cloud "
-                "Console. Verify the scopes in scripts/gmail_oauth_setup.py and the API enablement."
+                "Console. Verify the scopes in the Google OAuth provider config and the API enablement."
             )
         if status == 404:
             return (
@@ -482,9 +480,8 @@ def _gmail_status(args: dict | None = None) -> str:
     except Exception as e:
         return _status_report("❌", "AUTH_OR_API_ERROR", "action needed",
             f"The Gmail API did not respond to the probe call: {_format_google_error(e, 'Gmail')}",
-            ["Run scripts/gmail_oauth_setup.py to refresh / re-issue credentials.",
+             ["Re-authenticate via Skald's OAuth flow (Sign in from the connector page).",
              "If credentials are valid, verify the Gmail API is enabled in the Google Cloud Console."])
-
     email = profile.get("emailAddress", "?")
     return _status_report("✅", "READY", "ok",
         "Google Gmail integration is operational: credentials load, the access token refreshes "