Keep provider diagnostics and model lists in sync (#1660)

* fix(server): align provider catalog diagnostics

* fix(server): preserve catalog profile models

* refactor: unify provider catalog discovery under AgentClient.fetchCatalog

Remove listModels/listModes from AgentClient and fetchModels/fetchModes
from ProviderDefinition. All provider runtime discovery now flows through
a single fetchCatalog(options) => ProviderCatalog API.

ProviderSnapshotManager.listModels/listModes remain as cached snapshot
conveniences only. Provider implementations (acp, codex, opencode, pi,
claude, mock) updated accordingly; agent-manager default model resolution
now calls fetchCatalog.

Reshape step toward issue pi-model-list-empty.

* refactor: remove remaining provider listModels/listModes runtime API residue

Migrate remaining AgentClient/provider-client implementations and tests to
fetchCatalog. Remove obsolete ListModelsOptions/ListModesOptions interfaces.
Update ProviderSnapshotManager.getProviderDiagnostic to materialize clients
via ensureClient(provider, definition) so diagnostics self-heal the settings
sheet instead of failing when providerClients[provider] is absent.

Allowed to remain: ProviderSnapshotManager.listModels/listModes as cached
snapshot readers; protocol/client legacy list_provider_models names; unrelated
local helper in create-agent-mode.

* test(server): repair test clients after fetchCatalog refactor

- Restore TestAgentClient.fetchCatalog with proper model list and resumeSession.
- Restore NativeArchiveRecordingClient and EnvProbeAgentClient removed during refactor.
- Fix ResumeCaptureClient.fetchCatalog and resumeSession.
- Fix stream-coalescing TestAgentClient.fetchCatalog shape and isAvailable.
- Mock accessible OpenCode provider in full-access mode tests so fetchCatalog does not throw.

* refactor(app): update stable discovered models ref directly during render

docs/providers.md

@@ -34,7 +34,7 @@ OpenCode owns user message IDs. Do not pass Paseo-generated IDs to OpenCode prom
 
 Every provider adapter owns its canonical user-message timeline rows. When a foreground prompt is accepted, the adapter must emit exactly one `user_message` timeline item for that submitted prompt, using the same message ID it gives to or receives from the provider runtime. Optimistic client messages are UI-only and provider transcript echoes are optional; neither is allowed to be the only source of truth. If the provider later echoes the same submitted user message, dedupe by provider-visible message ID, not by text.
 
-Draft metadata lookups should avoid creating provider sessions when the upstream provider has top-level APIs for that metadata. Prefer `AgentClient.listModels`, `listModes`, `listCommands`, or `listFeatures` over creating a scratch `AgentSession`; scratch sessions can show up as empty native sessions in provider import/history UIs.
+Draft metadata lookups should avoid creating provider sessions when the upstream provider has top-level APIs for that metadata. Prefer `AgentClient.fetchCatalog`, `listCommands`, or `listFeatures` over creating a scratch `AgentSession`; scratch sessions can show up as empty native sessions in provider import/history UIs. `fetchCatalog` is the single discovery API for models and modes — provider implementations may use one process, separate upstream calls, or static data internally, but callers outside the provider do not get separate runtime model/mode probes.
 
 Provider session import has its own contract. The picker calls `listImportableSessions` and receives rows only: provider handle, cwd, title, prompt previews, and last activity. Import calls `importSession({ providerHandleId, cwd })` for the selected row and must not call listing again. The provider returns the resumed session, storage config, persistence handle, and hydrated timeline for that one native session; `AgentManager.importProviderSession` seeds the daemon timeline and publishes the Paseo agent only after it is ready.
 
@@ -336,14 +336,13 @@ interface AgentClient {
     overrides?: Partial<AgentSessionConfig>,
     launchContext?: AgentLaunchContext,
   ): Promise<AgentSession>;
-  listModels(options: ListModelsOptions): Promise<AgentModelDefinition[]>;
+  fetchCatalog(options: FetchCatalogOptions): Promise<ProviderCatalog>;
   isAvailable(): Promise<boolean>;
   // Optional:
-  listModes?(options: ListModesOptions): Promise<AgentMode[]>;
-  listImportableSessions?(
+  listImportableSessions(
     options?: ListImportableSessionsOptions,
   ): Promise<ImportableProviderSession[]>;
-  importSession?(
+  importSession(
     input: ImportProviderSessionInput,
     context: ImportProviderSessionContext,
   ): Promise<ImportedProviderSession>;