fix(spec): correct skill surface comment — ask is not the open-source/free surface

The JSDoc on SkillSchema.surface described the default `'ask'` value as "the
open-source/free surface." That is inaccurate: per cloud ADR-0025 the in-product
agent runtime for BOTH `ask` and `build` ships in the cloud / Enterprise
distribution (the open edition is MCP-only, BYO-AI). The `surface` value is
authoring metadata — which agent a skill binds to — not an edition gate.

Comment-only: the Zod `.describe()` string and the schema itself are unchanged,
so generated reference docs and runtime behavior are unaffected.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01LHQscZJ8NvXceSmsPNdTZd

Author: claude

packages/spec/src/ai/skill.zod.ts

@@ -77,7 +77,9 @@ export const SkillSchema = lazySchema(() => z.object({
    * matches either); the runtime enforces this at load time. An agent's
    * tool set is the union of its surface-compatible skills' tools — there
    * is no global fall-through (ADR-0064). Defaults to `'ask'`, the
-   * open-source/free surface.
+   * data-console surface. (Both the `ask` and `build` in-product agent
+   * runtimes ship in the cloud / Enterprise distribution per ADR-0025;
+   * the surface value here is authoring metadata, not an edition gate.)
    */
   surface: z.enum(['ask', 'build', 'both']).default('ask').describe(
     "Agent surface this skill binds to ('ask' | 'build' | 'both') — ADR-0063 §3",