Antispam: one button, and only where it means something

Spam / Not spam appeared on every message in every thread. "Not spam" on an
inbox message is nonsense — it was never filed as spam — and a pair of buttons
everywhere is noise that trains nobody.

The slot now shows a single action chosen by where the message actually is:
"Spam" in the inbox or archive, "Not spam" in the spam folder, nothing at all in
Sent, Drafts or Trash, where no move is a verdict about spam. A message already
taught says so instead of offering the same lesson again.

That needs the message's folder, which the slot was never told. Rather than a
core change to the slot props, /verdict/{id} becomes /context/{id} and returns
the folder alongside the verdict — one round-trip, answered for any message
including ones never classified.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_018SqJYt7jD7oUEkoY68sBZo

plugins/webmail_plugin_antispam/webmail_plugin_antispam/schemas.py

@@ -54,6 +54,19 @@ class VerdictOut(BaseModel):
     learned: str | None
 
 
+class MessageContextOut(BaseModel):
+    """What the per-message UI slots need in one round-trip.
+
+    ``special_use`` is where the message currently sits, which decides which
+    action is meaningful: "Spam" in the inbox, "Not spam" in the spam folder,
+    neither in Sent or Drafts.
+    """
+
+    message_id: uuid.UUID
+    special_use: str | None
+    verdict: VerdictOut | None
+
+
 class StatsOut(BaseModel):
     counts: dict[str, int]
     top_symbols: list[dict[str, object]]