ASB has no `SetBufferedUpdateInterval` analogue — the per-monitored-
item `MinimalMonitoredItem::sample_interval` plays the cadence-knob
role. Calling `subscribe_buffered` on an ASB session now returns
`Error::Unsupported { transport: TransportKind::Asb, operation: ... }`
synchronously, without touching the wire.
The error-construction logic is split into a free fn
`unsupported_subscribe_buffered_error()` so the gate's exact shape
is unit-testable without spinning up a live authenticator + transport
fake. New unit test asserts both the variant tag and that the
operation message names the unsupported method + hints at the
`sample_interval` analogue.
Workspace 758 → 759 tests, clippy clean.
Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
Joseph Doherty
34045c2f6d