feat(llm): interrogate a draft provider endpoint for its models

Once a pi-ai route became a declaration rather than a catalog lookup,
adding an OpenAI-compatible gateway meant knowing its model ids up
front. Most such endpoints publish that list at `GET /models`, but no
seam operation could ask: every one is keyed by a registered provider
route, and the provider being added has no route, no stored profile,
and no stored credential — the endpoint and key are values in a form.

Interrogation is therefore keyed by settings namespace, which a
configuration surface already holds from the configurable-provider
directory. `registerModelDiscovery` offers it per namespace,
`discoverModels` asks, and the request carries the draft itself. The
reply is candidates, not a catalog: every field but the id is optional
because most listings disclose nothing else, and adopting one is a
settings write like any other. Nothing here reads or writes settings or
credentials, so `settings.yaml` still decides what a route serves.

`llm.discoverModels` carries the same draft over the wire. Its apiKey is
the third and last payload a secret may ride, and it is never stored,
logged, or echoed; every refusal folds into `model-discovery-failed`,
naming the endpoint asked but never the credential offered.

The pi-ai side is a plain GET for OpenAI-compatible protocols only —
their listing shape is the one gateways, self-hosted servers, and the
official endpoints agree on. Others say so, sending the user to
hand-entry rather than reporting a guessed shape as an empty provider.
The reply is read under a four-megabyte ceiling held on the bytes
actually received, because the endpoint is a URL the user typed.

docs/cordis-catalog/services.md

@@ -834,9 +834,9 @@ listProviders(): LlmProviderInfo[]
  * entry, or a provider already declared by any registration throws
  * `LlmError` without registering the rest. Disposed with the fiber.
  * @param entries - every configurable provider this plugin owns.
- * @returns a handle that withdraws all of them, and can atomically replace them.
+ * @returns the disposer that withdraws all of them.
  */
-registerConfigurableProviders(entries: readonly LlmConfigurableProvider[]): DirectoryRegistrationHandle
+registerConfigurableProviders(entries: readonly LlmConfigurableProvider[]): () => void
 
 /**
  * List every declared configurable provider, registered or dormant.
@@ -844,6 +844,36 @@ registerConfigurableProviders(entries: readonly LlmConfigurableProvider[]): Dire
  */
 listConfigurableProviders(): LlmConfigurableProvider[]
 
+/**
+ * Offer to interrogate provider endpoints on behalf of the settings
+ * namespace this plugin owns. The namespace is the key because that is what
+ * a configuration surface already holds from the configurable-provider
+ * directory, and because a provider being *added* has no route to name yet.
+ * Disposed with the fiber.
+ * @param settingsNs - the namespace whose profiles this discovery serves.
+ * @param discover - interrogates one endpoint; must honor `request.signal`.
+ * @returns the disposer that withdraws the offer.
+ */
+registerModelDiscovery( settingsNs: string, discover: (request: LlmModelDiscoveryRequest) => Promise<readonly LlmDiscoveredModel[]>, ): () => void
+
+/**
+ * List the settings namespaces that can interrogate a provider endpoint, so
+ * a surface can offer the action only where it will work.
+ * @returns the namespaces in registration order.
+ */
+listModelDiscoveryNamespaces(): string[]
+
+/**
+ * Interrogate one provider endpoint for the models it advertises. The
+ * request describes a draft, not a stored route, so nothing here reads or
+ * writes settings or credentials — the caller owns both, and the reply is
+ * candidate metadata a surface may offer for adoption.
+ * @param settingsNs - namespace whose registered discovery serves this draft.
+ * @param request - the endpoint, protocol, and one-shot credential to use.
+ * @returns the advertised models, deduplicated in endpoint order.
+ */
+async discoverModels( settingsNs: string, request: LlmModelDiscoveryRequest, ): Promise<LlmDiscoveredModel[]>
+
 /**
  * Resolve the retry policy captured when one provider route was registered.
  * @param provider - registered provider route to inspect.
@@ -908,9 +938,9 @@ async prepareCall(config: LlmCallConfig, signal?: AbortSignal): Promise<Prepared
 stream(options: GenerateOptions): AsyncIterable<StreamChunk>
 ```
 
-Types: [AdapterRegistrationHandle](../core-data-structures/core.md) · [DirectoryRegistrationHandle](../core-data-structures/core.md) · [GenerateOptions](../core-data-structures/core.md) · [LlmAdapter](../core-data-structures/llm-streaming.md) · [LlmCallConfig](../core-data-structures/core.md) · [LlmConfigurableProvider](../core-data-structures/core.md) · [LlmModelInfo](../core-data-structures/core.md) · [LlmProviderInfo](../core-data-structures/core.md) · [LlmResolvedModelInfo](../core-data-structures/core.md) · [PreparedLlmCall](../core-data-structures/llm-streaming.md) · [ResolvedRetryPolicy](../core-data-structures/llm-streaming.md) · [StreamChunk](../core-data-structures/llm-streaming.md)
+Types: [AdapterRegistrationHandle](../core-data-structures/core.md) · [GenerateOptions](../core-data-structures/core.md) · [LlmAdapter](../core-data-structures/llm-streaming.md) · [LlmCallConfig](../core-data-structures/core.md) · [LlmConfigurableProvider](../core-data-structures/core.md) · [LlmDiscoveredModel](../core-data-structures/core.md) · [LlmModelDiscoveryRequest](../core-data-structures/core.md) · [LlmModelInfo](../core-data-structures/core.md) · [LlmProviderInfo](../core-data-structures/core.md) · [LlmResolvedModelInfo](../core-data-structures/core.md) · [PreparedLlmCall](../core-data-structures/llm-streaming.md) · [ResolvedRetryPolicy](../core-data-structures/llm-streaming.md) · [StreamChunk](../core-data-structures/llm-streaming.md)
 
-Source: [`packages/llm/llm/src/index.ts:253`](../../packages/llm/llm/src/index.ts)
+Source: [`packages/llm/llm/src/index.ts:234`](../../packages/llm/llm/src/index.ts)
 
 ## `ctx.permission` — `PermissionService`