Function declareUnavailable

declareUnavailable(id: string, motif: string): void
Records that a capability was asked for and is not available, and notifies subscribers.

Idempotent per id: the first motif is kept, later calls for the same id do nothing and notify nobody.
Parameters
- id: string
  Capability id, as it would have been passed to CapabilityRegistry.register().
- motif: string
  Why it is unavailable, in one sentence — this is what a host displays.
Returns void
Example
```
GeoLeaf?.Capabilities?.declareUnavailable(
    "offline",
    "the bundle does not embark it"
);
```
- Defined in packages/core/src/kernel/api/unavailable-capabilities.ts:79