fix(coderd): handle ignored errors across coderd packages (#22851)

Handle previously ignored error return values in coderd:

- coderd/chats.go: check sendEvent errors, log on failure
- coderd/chatd/chattest: thread testing.TB through server structs,
  replace log.Printf with t.Logf, check writeSSEEvent errors
- coderd/chatd/chattool/createworkspace.go: log UpdateChatWorkspace
  failure instead of discarding both return values
- coderd/chatd/chattool/execute.go: surface ProcessOutput error in
  the timeout message returned to the caller
- coderd/provisionerdserver: log stream.Send failure in the
  DownloadFile error helper

coderd/chatd/chattool/createworkspace.go

@@ -12,6 +12,7 @@ import (
 	"github.com/google/uuid"
 	"golang.org/x/xerrors"
 
+	"cdr.dev/slog/v3"
 	"github.com/coder/coder/v2/coderd/database"
 	"github.com/coder/coder/v2/coderd/util/namesgenerator"
 	"github.com/coder/coder/v2/codersdk"
@@ -67,6 +68,7 @@ type CreateWorkspaceOptions struct {
 	CreateFn    CreateWorkspaceFn
 	AgentConnFn AgentConnFunc
 	WorkspaceMu *sync.Mutex
+	Logger      slog.Logger
 }
 
 type createWorkspaceArgs struct {
@@ -192,13 +194,19 @@ func CreateWorkspace(options CreateWorkspaceOptions) fantasy.AgentTool {
 
 			// Persist workspace + agent association on the chat.
 			if options.DB != nil && options.ChatID != uuid.Nil {
-				_, _ = options.DB.UpdateChatWorkspace(ctx, database.UpdateChatWorkspaceParams{
+				if _, err := options.DB.UpdateChatWorkspace(ctx, database.UpdateChatWorkspaceParams{
 					ID: options.ChatID,
 					WorkspaceID: uuid.NullUUID{
 						UUID:  workspace.ID,
 						Valid: true,
 					},
-				})
+				}); err != nil {
+					options.Logger.Warn(ctx, "failed to persist chat workspace association",
+						slog.F("chat_id", options.ChatID),
+						slog.F("workspace_id", workspace.ID),
+						slog.Error(err),
+					)
+				}
 			}
 
 			// Wait for the agent to come online and startup scripts to finish.

coderd/chatd/chattool/execute.go

@@ -245,14 +245,18 @@ func pollProcess(
 				context.Background(),
 				5*time.Second,
 			)
-			outputResp, _ := conn.ProcessOutput(bgCtx, processID)
+			outputResp, outputErr := conn.ProcessOutput(bgCtx, processID)
 			bgCancel()
 			output := truncateOutput(outputResp.Output)
+			timeoutMsg := fmt.Sprintf("command timed out after %s", timeout)
+			if outputErr != nil {
+				timeoutMsg += fmt.Sprintf(" (failed to get output: %v)", outputErr)
+			}
 			return ExecuteResult{
 				Success:   false,
 				Output:    output,
 				ExitCode:  -1,
-				Error:     fmt.Sprintf("command timed out after %s", timeout),
+				Error:     timeoutMsg,
 				Truncated: outputResp.Truncated,
 			}
 		case <-ticker.C: