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/src/features/feature-configurator.ts

@@ -26,6 +26,7 @@ export class FeatureConfigurator {
    * @param current - currently installed selection, when configuring.
    * @param prefilledOptions - options already chosen by a tree picker.
    * @param prefilledSecrets - non-interactive secret values supplied by creation.
+   * @param prefilledValues - non-interactive value inputs supplied by a headless spec.
    * @returns normalized selection with captured values and secrets.
    */
   async configure(
@@ -34,6 +35,7 @@ export class FeatureConfigurator {
     current?: FeatureSelection,
     prefilledOptions?: readonly string[],
     prefilledSecrets: Readonly<Record<string, string>> = {},
+    prefilledValues: Readonly<Record<string, unknown>> = {},
   ): Promise<FeatureSelection> {
     let options: readonly string[]
     switch (feature.mode) {
@@ -69,6 +71,11 @@ export class FeatureConfigurator {
       id: feature.id,
       options,
     }
+    const coercedPrefilled: Record<string, string> = {}
+    for (const [key, value] of Object.entries(prefilledValues)) {
+      if (typeof value !== 'string') throw new Error(`${feature.id}.${key} value must be a string`)
+      coercedPrefilled[key] = value
+    }
     const values: Record<string, string> = {}
     for (const input of feature.valueInputs(selected, profile)) {
       const existing = current?.values?.[input.id]
@@ -81,7 +88,7 @@ export class FeatureConfigurator {
         ...existing === undefined ? {} : { initialValue: existing },
         validate: value => value.trim().length === 0 ? 'A value is required' : undefined,
       })
-      values[input.id] = requireAnswer(await question.resolve(this.port))
+      values[input.id] = requireAnswer(await question.resolve(this.port, coercedPrefilled[input.id]))
     }
     const base: FeatureSelection = Object.keys(values).length === 0
       ? selected

packages/sdk/helper/src/index.ts

@@ -43,3 +43,4 @@ export {
 } from './questions/question.ts'
 export type { Question } from './questions/question.ts'
 export { ClackPromptPort } from './questions/clack-prompt-port.ts'
+export { HeadlessPromptError, HeadlessPromptPort } from './questions/headless-prompt-port.ts'

packages/sdk/helper/src/questions/headless-prompt-port.ts

@@ -0,0 +1,97 @@
+/**
+ * Non-interactive prompt port for headless create/config and skill-driven runs.
+ *
+ * @module @deepseek-ai/dsh-helper/questions/headless-prompt-port
+ */
+
+import type {
+  ConfirmPromptRequest,
+  MultiSelectPromptRequest,
+  NestedMultiSelectRequest,
+  NestedMultiSelectValue,
+  PromptOutcome,
+  PromptPort,
+  SecretPromptRequest,
+  SelectPromptRequest,
+  TextPromptRequest,
+} from './prompt-port.ts'
+
+/**
+ * Raised when a headless run reaches a decision that was neither prefilled nor
+ * carries a usable default. The message names the unanswered prompt so an agent
+ * or CI caller can see exactly which input the spec must supply.
+ */
+export class HeadlessPromptError extends Error {
+  /** The unanswered prompt's user-facing message. */
+  readonly prompt: string
+
+  /** Build an error naming the unanswered prompt. */
+  constructor(prompt: string) {
+    super(`headless run needs an answer for: ${prompt}`)
+    this.name = 'HeadlessPromptError'
+    this.prompt = prompt
+  }
+}
+
+/** Resolve an answered outcome. */
+function answered<T>(value: T): Promise<PromptOutcome<T>> {
+  return Promise.resolve({ status: 'answered', value })
+}
+
+/** Reject with a named unanswered-prompt error. */
+function unanswered<T>(message: string): Promise<PromptOutcome<T>> {
+  return Promise.reject(new HeadlessPromptError(message))
+}
+
+/**
+ * A {@link PromptPort} that never blocks on a terminal.
+ *
+ * Answers are expected to arrive as prefilled values through the `Question` /
+ * `FeatureConfigurator` layers, so in a fully specified run this port is never
+ * reached. When it *is* reached, it takes the prompt's own declared default
+ * (`defaultValue` / `initialValue`) if one exists; otherwise it fails loud with
+ * {@link HeadlessPromptError}. Nested feature selection has no scalar default,
+ * so it always fails loud — headless callers must supply the feature set through
+ * the spec rather than the tree picker.
+ */
+export class HeadlessPromptPort implements PromptPort {
+  /** Answer visible text from its default, or fail loud. */
+  text(request: TextPromptRequest): Promise<PromptOutcome<string>> {
+    const fallback = request.initialValue ?? request.defaultValue
+    if (fallback === undefined) return unanswered(request.message)
+    const diagnostic = request.validate?.(fallback)
+    if (diagnostic) return unanswered(`${request.message} (${diagnostic})`)
+    return answered(fallback)
+  }
+
+  /** A secret has no safe default: always fail loud. */
+  secret(request: SecretPromptRequest): Promise<PromptOutcome<string>> {
+    return unanswered(request.message)
+  }
+
+  /** Answer a single choice from its initial value, or fail loud. */
+  select<T>(request: SelectPromptRequest<T>): Promise<PromptOutcome<T>> {
+    if (request.initialValue === undefined) return unanswered(request.message)
+    return answered(request.initialValue)
+  }
+
+  /** Answer a multi-choice from its initial values, or fail loud when required. */
+  multiselect<T>(request: MultiSelectPromptRequest<T>): Promise<PromptOutcome<readonly T[]>> {
+    const initial = request.initialValues ?? []
+    if (request.required && initial.length === 0) return unanswered(request.message)
+    return answered(initial)
+  }
+
+  /** Answer a confirmation from its initial value, or fail loud. */
+  confirm(request: ConfirmPromptRequest): Promise<PromptOutcome<boolean>> {
+    if (request.initialValue === undefined) return unanswered(request.message)
+    return answered(request.initialValue)
+  }
+
+  /** Nested feature selection has no scalar default: always fail loud. */
+  nestedMultiselect<TValue, TChoice>(
+    request: NestedMultiSelectRequest<TValue, TChoice>,
+  ): Promise<PromptOutcome<readonly NestedMultiSelectValue<TValue, TChoice>[]>> {
+    return unanswered(request.message)
+  }
+}