style: apply gofmt

Estate-wide consolidation pass. golangci-lint v2 default set enables NO
formatter, so gofmt drift accumulated silently across the estate -- 8 repos
were carrying it, this one included. Same hole that let two files rot in
dma-cli until they were found by hand (dma-cli#12).

Mechanical and deterministic: `gofmt -w`, nothing hand-edited. Verified
before commit -- gofmt -l now reports 0, go build and go vet both pass.

Clears this repo to adopt the canonical .golangci.yml (infra
ci-templates/golangci.yml, infra#309 pattern) in a later wave.

ingestion/internal/audit/degrading_test.go

@@ -46,10 +46,10 @@ func (f *fakeNotifier) Notify(_ context.Context, msg string) error {
 // unwritableBuffer always reports it cannot be written (floor condition).
 type unwritableBuffer struct{}
 
-func (unwritableBuffer) Writable() error                       { return errors.New("disk full") }
-func (unwritableBuffer) Append(capture.AuditEntry) error       { return errors.New("disk full") }
-func (unwritableBuffer) Pending() ([]audit.Buffered, error)    { return nil, nil }
-func (unwritableBuffer) Confirm(string) error                  { return nil }
+func (unwritableBuffer) Writable() error                    { return errors.New("disk full") }
+func (unwritableBuffer) Append(capture.AuditEntry) error    { return errors.New("disk full") }
+func (unwritableBuffer) Pending() ([]audit.Buffered, error) { return nil, nil }
+func (unwritableBuffer) Confirm(string) error               { return nil }
 
 func newFileBuffer(t *testing.T) *audit.FileBuffer {
 	t.Helper()