refactor: make Avatar repository own Pages deployment

[NWYLZW]

Move Avatar Pages deployment ownership into oneworks-ai/avatar.

• remove the app-side cross-repository deploy trigger and AVATAR_DEPLOY_TOKEN dependency
• document Avatar CI-to-Pages ownership and anti-regression rules
• keep app as a shared build dependency, not the Avatar release-version selector
• retain the stable Avatar surface-marking and design-memory guidance

Supersedes #110.

Experience Review

• 已判断是否需要沉淀经验
• 如需要，已运行 $post-task-experience-review
• reviewer PASS / NOT APPLICABLE 后才进入 merge

Policy Conflict Review

• Independent read-only reviewer checked workflow, permission, and release-rule conflicts and reported PASS

[vercel]

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Project	Deployment	Actions	Updated (UTC)
oneworks-dev	Ready	Preview	Aug 27, 2026 1:40pm

[github-actions]

Experience Review

Before merge, make sure the PR body contains this completed checklist:

## Experience Review
- [x] 已判断是否需要沉淀经验
- [x] 如需要，已运行 `$post-task-experience-review`
- [x] reviewer `PASS` / `NOT APPLICABLE` 后才进入 merge

Checklist to confirm:

• Decide whether this PR produced reusable project experience.
• If experience should be captured, run $post-task-experience-review.
• Merge only after the independent reviewer reports PASS or NOT APPLICABLE for the Experience Review Result.
• For workflow, permission, or release-rule documentation changes, also add this checked section to the PR body after an independent read-only conflict review:

## Policy Conflict Review
- [x] Independent read-only reviewer checked workflow, permission, and release-rule conflicts and reported PASS