fix(watcher): never walk into raw/rejected/ — brain_reject (closes #81)

Adds brain_reject (RejectNote + MCP tool) and fixes the watcher to skip raw/rejected/, preventing declined notes from being silently re-ingested and republished.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>
Co-authored-by: Mathias <mthbqv@gmail.com>

ingestion/internal/mcp/server_test.go

@@ -58,7 +58,7 @@ func TestServerToolsList(t *testing.T) {
 	}
 	assert.ElementsMatch(t, []string{
 		"brain_query", "brain_write", "brain_update", "brain_get",
-		"brain_pending", "brain_promote",
+		"brain_pending", "brain_promote", "brain_reject",
 		"brain_read", "brain_edit",
 		"brain_tunnel",
 		"brain_ingest_raw", "brain_ingest",