fix(llm-pi-ai): let a model declare the request modalities it accepts

A model the installed pi-ai catalog does not describe was reported as
text-only with no way to say otherwise, so a vision model added through
the custom-provider form was refused at every image admission point.
The justification in the source described the DeepSeek chat-completions
serializer, which does reject image blocks; the pi-ai request converter
and every wire protocol it speaks carry images.

Modalities now resolve entry `input` -> installed catalog entry -> route
`defaultInput`, the chain the two capacity fallbacks already use, so the
route value is a fallback and never narrows a catalog model. Its default
stays `[text]`: nothing can interrogate a gateway for its modalities, and
over-claiming admits an image the provider rejects mid-turn, after prompt
admission has already committed the message.

packages/llm/llm-pi-ai/tests/catalog.spec.ts

@@ -186,6 +186,75 @@ describe('hand-declared providers', () => {
     expect(resolved.get('acme-gateway')?.configuredMaxTokens.get('sized')).toBe(512)
   })
 
+  it('takes a model’s declared modalities, then the catalog’s, then the route’s', () => {
+    const vision = getBuiltinModels('anthropic').find(model => model.input.includes('image'))
+    if (vision === undefined) throw new Error('the installed catalog ships no anthropic vision model')
+    const resolved = resolveProfiles({
+      'acme-gateway': {
+        api: 'openai-completions',
+        baseURL: 'https://acme.test',
+        // One route, two modality sets: the entry field is what says so.
+        models: [{ id: 'bare' }, { id: 'seeing', input: ['text', 'image'] }, { id: 'deaf', input: ['text'] }],
+      },
+      'seeing-gateway': {
+        api: 'openai-completions',
+        baseURL: 'https://seeing.test',
+        // A gateway whose undescribed models all take images says so once
+        // rather than on every entry; an entry still outranks it.
+        defaultInput: ['text', 'image'],
+        models: [{ id: 'bare' }, { id: 'deaf', input: ['text'] }],
+      },
+      // The route value is a fallback, never an override: a catalog model
+      // keeps what the catalog records even under a narrower route default,
+      // exactly as it keeps its own contextWindow.
+      'anthropic': { defaultInput: ['text'] },
+    })
+    const inputOf = (route: string, id: string): readonly string[] | undefined =>
+      resolved.get(route)?.piProvider.getModels().find(model => model.id === id)?.input
+
+    // Nothing can interrogate the endpoint, so an undeclared model on a route
+    // that names no default claims only the modality every supported protocol
+    // carries. Claiming images instead would admit one the provider then
+    // rejects mid-turn, after the durable message is already in the log.
+    expect(inputOf('acme-gateway', 'bare')).toEqual(['text'])
+    expect(inputOf('acme-gateway', 'seeing')).toEqual(['text', 'image'])
+    expect(inputOf('acme-gateway', 'deaf')).toEqual(['text'])
+    expect(inputOf('seeing-gateway', 'bare')).toEqual(['text', 'image'])
+    expect(inputOf('seeing-gateway', 'deaf')).toEqual(['text'])
+    expect(inputOf('anthropic', vision.id)).toEqual(vision.input)
+  })
+
+  it('reads an entry’s empty modality list as no answer, and the route’s as unserviceable', () => {
+    // Absent and empty are the same request on an entry, exactly as they are
+    // for the route's `models` list — which matters because the config schema
+    // materializes `[]` for an absent array, so an entry naming a catalog
+    // model without declaring modalities must keep the catalog's rather than
+    // describe a model that accepts nothing.
+    const [catalogModel] = getBuiltinModels('deepseek')
+    if (catalogModel === undefined) throw new Error('the installed catalog ships no deepseek model')
+    const resolved = resolveProfiles({
+      'deepseek': { baseURL: 'https://catalog.test', models: [{ id: catalogModel.id, input: [] }] },
+      'acme-gateway': {
+        api: 'openai-completions',
+        baseURL: 'https://acme.test',
+        models: [{ id: 'bare', input: [] }],
+      },
+    })
+    expect(resolved.get('acme-gateway')?.piProvider.getModels()[0]?.input).toEqual(['text'])
+    expect(resolved.get('deepseek')?.piProvider.getModels()[0]?.input).toEqual(catalogModel.input)
+
+    // Nothing sits below the route value, so its empty list states no answer
+    // anything could take, and is refused where it is written.
+    expect(() => resolveProfiles({
+      'acme-gateway': {
+        api: 'openai-completions',
+        baseURL: 'https://acme.test',
+        defaultInput: [],
+        models: [{ id: 'bare' }],
+      },
+    })).toThrow(/defaultInput must name at least one modality/)
+  })
+
   it('rejects a model the route cannot identify', () => {
     const declare = (model: LlmPiAi.PiAiModelProfile): (() => unknown) =>
       () => resolveProfiles({ 'acme-gateway': { api: 'openai-completions', baseURL: 'https://acme.test', models: [model] } })