fix(scouts): fetch single Gmail message instead of bulk in fetch_content

Replace bulk GmailClient.fetch_messages() + linear search with a direct
service.users().messages().get(format="full") call. Adds _extract_plain_text_body
helper for recursive MIME part walking. Update test to patch _get_gmail_service.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

app/scouts/connectors/gmail.py

@@ -16,12 +16,35 @@ from datetime import datetime, timezone
 
 from app.config.settings import settings
 from app.integrations import decrypt_token
-from app.integrations.gmail import GmailClient
 from app.scouts.connectors.base import ItemContent, ItemMetadata, ItemRef
 
 logger = logging.getLogger(__name__)
 
 
+def _extract_plain_text_body(payload: dict) -> str:
+    """Recursively walk a Gmail message payload to find text/plain content."""
+    import base64
+    mime_type = payload.get("mimeType", "")
+    if mime_type == "text/plain":
+        data = payload.get("body", {}).get("data", "")
+        if data:
+            return base64.urlsafe_b64decode(data + "==").decode("utf-8", errors="replace")
+        return ""
+    if mime_type.startswith("multipart/"):
+        for part in payload.get("parts", []):
+            text = _extract_plain_text_body(part)
+            if text:
+                return text
+    # text/html fallback: strip tags rudimentarily if no text/plain part
+    if mime_type == "text/html":
+        data = payload.get("body", {}).get("data", "")
+        if data:
+            import re
+            html = base64.urlsafe_b64decode(data + "==").decode("utf-8", errors="replace")
+            return re.sub(r"<[^>]+>", " ", html)
+    return ""
+
+
 def _get_gmail_service(scout):
     """Return a synchronous Google API client for low-level metadata/history calls."""
     from googleapiclient.discovery import build
@@ -118,32 +141,27 @@ class GmailConnector:
     # ── fetch_content ─────────────────────────────────────────────────────
 
     async def fetch_content(self, scout, ref: ItemRef) -> ItemContent:
-        """Fetch full body text via GmailClient — transient, must not be persisted."""
-        creds_info = decrypt_token(scout.oauth_token_encrypted)
-        client = GmailClient(creds_info)
-        # fetch_messages returns EmailMessage dataclasses with body_text already
-        # extracted and decoded. We pass an empty filter to avoid narrowing by
-        # date — callers should only invoke fetch_content for known-new messages.
-        messages = await client.fetch_messages(filter_config=None, since=None)
+        """Fetch full body text for a single message — transient, must not be persisted."""
 
-        # Pick the message matching our ref (or fall back to first if only one returned).
-        email_msg = next(
-            (m for m in messages if m.id == ref.source_msg_ref),
-            messages[0] if messages else None,
-        )
-        if email_msg is None:
-            raise ValueError(f"Message {ref.source_msg_ref!r} not found via GmailClient")
+        def _sync() -> ItemContent:
+            service = _get_gmail_service(scout)
+            msg = service.users().messages().get(
+                userId="me", id=ref.source_msg_ref, format="full",
+            ).execute()
+            headers = {h["name"]: h["value"] for h in msg.get("payload", {}).get("headers", [])}
+            body_text = _extract_plain_text_body(msg.get("payload", {}))
+            return ItemContent(
+                metadata=ItemMetadata(
+                    subject=headers.get("Subject"),
+                    sender=headers.get("From"),
+                    snippet=msg.get("snippet"),
+                    received_at=None,
+                ),
+                body_text=body_text,
+                raw_headers=headers,
+            )
 
-        return ItemContent(
-            metadata=ItemMetadata(
-                subject=email_msg.subject,
-                sender=email_msg.sender,
-                snippet=None,
-                received_at=email_msg.date,
-            ),
-            body_text=email_msg.body_text,
-            raw_headers={},
-        )
+        return await asyncio.to_thread(_sync)
 
     # ── archive ───────────────────────────────────────────────────────────