feat(coderd/database): add error columns to aibridge interception records (#26960)

Adds a nullable `aibridge_interception_error_type` enum and an
`error_message` column to `aibridge_interceptions`, so a failed
interception's terminal upstream error can be persisted.

Schema only: the write path and API exposure land in the stacked
backend PR.

*This PR was produced by opencode (agent) using the `anthropic/claude-opus-4-8` model, under human direction and review.*

coderd/database/modelqueries.go

@@ -1151,6 +1151,8 @@ func (q *sqlQuerier) ListAuthorizedAIBridgeSessionThreads(ctx context.Context, a
 			&i.AIBridgeInterception.CredentialHint,
 			&i.AIBridgeInterception.AgentFirewallSessionID,
 			&i.AIBridgeInterception.AgentFirewallSequenceNumber,
+			&i.AIBridgeInterception.ErrorType,
+			&i.AIBridgeInterception.ErrorMessage,
 		); err != nil {
 			return nil, err
 		}