Phase 3a: Peripheral discovery filter + service/characteristic discovery + catalog snapshots

[itsniper]

Parent: #52

Requirements

• Sticky discovery filter on Peripheral (services/chars); fail-closed if empty when auto-discovery required (FR-10.1.2).
• Define what counts as an "auto-discovery path." Peripheral.connect(autoReconnect:) registers a manual-connect hold and links without any discovery today. Decide and document whether a manual connect with an empty filter is a hard error or a link-only operation. Recommended: manual connect links without discovering; auto-discovery is triggered by work (or an explicit on-demand discover()), so declaring a filter is required only where discovery actually runs.
• Filter must be settable before the peripheral is ever connected — a manual connect() can throw bluetoothPoweredOff while still recording durable demand, so filter declaration cannot depend on a live link.
• Filtered discover services → characteristics (ordering FR-10.2.1); per-service completion tracking.
• Sendable service/characteristic snapshots; no live CB in public API.
• Attach CBPeripheralDelegate inside the Bluetooth actor (incl. restore re-wire).

Acceptance criteria

• Filter API sticky on handle, settable before first connection
• Auto-discovery trigger points enumerated; empty filter on those paths = hard error
• Manual-connect-with-empty-filter behavior documented and tested
• Catalog snapshots exposed; CB types not public
• Tests with mocks for discovery happy path