feat(sdk): headless PromptPort + create/config headless plan

Add HeadlessPromptPort (fail-loud non-interactive PromptPort), thread
prefilled feature values through FeatureConfigurator, and let CreateWizard
and ConfigWorkflow accept a headless feature plan that skips the interactive
tree/suggests prompts. Per-file 100% coverage on all changed files.

packages/sdk/helper/tests/headless-prompt-port.spec.ts

@@ -0,0 +1,95 @@
+import { describe, expect, it } from 'vitest'
+import { HeadlessPromptError, HeadlessPromptPort } from '../src/questions/headless-prompt-port.ts'
+
+/** Unwrap an answered outcome or fail the test. */
+async function answered<T>(promise: Promise<{ status: 'answered'; value: T } | { status: 'cancelled' }>): Promise<T> {
+  const outcome = await promise
+  if (outcome.status !== 'answered') throw new Error('expected an answered outcome')
+  return outcome.value
+}
+
+describe('HeadlessPromptError', () => {
+  it('names the unanswered prompt', () => {
+    const error = new HeadlessPromptError('DeepSeek API key')
+    expect(error).toBeInstanceOf(Error)
+    expect(error.name).toBe('HeadlessPromptError')
+    expect(error.prompt).toBe('DeepSeek API key')
+    expect(error.message).toContain('DeepSeek API key')
+  })
+})
+
+describe('HeadlessPromptPort', () => {
+  const port = new HeadlessPromptPort()
+
+  describe('text', () => {
+    it('takes the initial value when present', async () => {
+      expect(await answered(port.text({ message: 'name', initialValue: 'agent' }))).toBe('agent')
+    })
+
+    it('falls back to the default value', async () => {
+      expect(await answered(port.text({ message: 'dir', defaultValue: 'my-agent' }))).toBe('my-agent')
+    })
+
+    it('prefers the initial value over the default value', async () => {
+      expect(await answered(port.text({ message: 'dir', initialValue: 'given', defaultValue: 'my-agent' }))).toBe('given')
+    })
+
+    it('fails loud when no default exists', async () => {
+      await expect(port.text({ message: 'base URL' })).rejects.toThrow(HeadlessPromptError)
+    })
+
+    it('fails loud when the default is invalid', async () => {
+      await expect(port.text({
+        message: 'name',
+        defaultValue: '',
+        validate: value => value.length === 0 ? 'required' : undefined,
+      })).rejects.toThrow(/required/)
+    })
+  })
+
+  describe('secret', () => {
+    it('always fails loud', async () => {
+      await expect(port.secret({ message: 'API key' })).rejects.toThrow(HeadlessPromptError)
+    })
+  })
+
+  describe('select', () => {
+    it('takes the initial value when present', async () => {
+      expect(await answered(port.select({ message: 'pm', options: [{ value: 'npm', label: 'npm' }], initialValue: 'npm' }))).toBe('npm')
+    })
+
+    it('fails loud without an initial value', async () => {
+      await expect(port.select({ message: 'pm', options: [{ value: 'npm', label: 'npm' }] })).rejects.toThrow(HeadlessPromptError)
+    })
+  })
+
+  describe('multiselect', () => {
+    it('returns the initial values', async () => {
+      expect(await answered(port.multiselect({ message: 'x', options: [], initialValues: ['a', 'b'] }))).toEqual(['a', 'b'])
+    })
+
+    it('returns an empty selection when none are supplied and none are required', async () => {
+      expect(await answered(port.multiselect({ message: 'x', options: [] }))).toEqual([])
+    })
+
+    it('fails loud when required and nothing is preselected', async () => {
+      await expect(port.multiselect({ message: 'x', options: [], required: true })).rejects.toThrow(HeadlessPromptError)
+    })
+  })
+
+  describe('confirm', () => {
+    it('takes the initial value when present', async () => {
+      expect(await answered(port.confirm({ message: 'install?', initialValue: false }))).toBe(false)
+    })
+
+    it('fails loud without an initial value', async () => {
+      await expect(port.confirm({ message: 'apply?' })).rejects.toThrow(HeadlessPromptError)
+    })
+  })
+
+  describe('nestedMultiselect', () => {
+    it('always fails loud', async () => {
+      await expect(port.nestedMultiselect({ message: 'Select features', options: [] })).rejects.toThrow(HeadlessPromptError)
+    })
+  })
+})

packages/sdk/helper/tests/questions.spec.ts

@@ -450,4 +450,35 @@ describe('feature configurator', () => {
     await expect(new FeatureConfigurator(new QueuePromptPort([])).configure(new EmptyExclusive(), profile))
       .rejects.toThrow('has no default option')
   })
+
+  it('configures fully from prefilled options, values, and secrets without prompting', async () => {
+    const registry = createBuiltinRegistry(profile)
+    const port = new QueuePromptPort([])
+    const result = await new FeatureConfigurator(port).configure(
+      registry.get(featureId('provider')),
+      profile,
+      undefined,
+      ['custom'],
+      { apiKey: 'prefilled-key' },
+      { baseURL: 'https://prefilled' },
+    )
+    expect(result).toMatchObject({
+      options: ['custom'],
+      values: { baseURL: 'https://prefilled' },
+      secrets: { apiKey: 'prefilled-key' },
+    })
+    expect(port.requests).toEqual([])
+  })
+
+  it('rejects a non-string prefilled feature value', async () => {
+    const registry = createBuiltinRegistry(profile)
+    await expect(new FeatureConfigurator(new QueuePromptPort([])).configure(
+      registry.get(featureId('provider')),
+      profile,
+      undefined,
+      ['custom'],
+      { apiKey: 'k' },
+      { baseURL: 123 },
+    )).rejects.toThrow('must be a string')
+  })
 })