feat(genomic): add skills field to BoilerplateConfig

[pyramation]

Summary

Adds BoilerplateSkill type and optional skills field to genomic's base BoilerplateConfig, so any CLI built on genomic can declare agent skills for post-scaffold installation.

export interface BoilerplateSkill {
  source: string;   // GitHub org/repo or full URL
  skills: string[]; // skill names to install
}

export interface BoilerplateConfig {
  type?: string;
  questions?: Question[];
  skills?: BoilerplateSkill[];  // ← new
}

Template .boilerplate.json files can now declare skills:

{
  "type": "workspace",
  "skills": [
    { "source": "constructive-io/constructive", "skills": ["pgpm"] }
  ]
}

Callers read result.config?.skills after scaffold() or inspect() and handle the actual npx skills add invocations themselves — genomic stays a pure scaffolding library with no child-process spawning.

Companion PRs:

• feat(pgpm): install skills from .boilerplate.json after scaffold constructive#1271 (merged) — pgpm CLI installSkills() consumer
• feat: declare skills in workspace .boilerplate.json pgpm-boilerplates#32 — workspace template declares skills

Link to Devin session: https://app.devin.ai/sessions/8a70e4bc95b947faa41db21e02ed818e
Requested by: @pyramation

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