feat(release): user-facing bilingual digest for release notes - #9216

What this PR does

Stable release notes currently read as a developer-facing list of pull requests bucketed by commit type. This PR turns the finalize step into a user-facing digest: the model now groups the release's changes into a few capability themes, each with a short intro and plain-language items, and the full pull-request list moves into a collapsed appendix with uniformly normalized titles. Highlights and themes are mirrored into a Chinese digest below a divider, and screenshots already present in merged pull-request bodies are attached to their digest items (host allowlist, capped per entry and per release). The changelog generator accepts the new marker version and embeds the digest, unwrapping the collapsed appendix and dropping images so CHANGELOG.md stays plain text. Every model failure keeps a working output: a failed themes call falls back to today's layout, invalid translations fall back to English with a run warning, and a model-less run reproduces today's notes byte for byte.

Why it's needed

The current notes are hard for users to scan: entries are grouped by change type rather than by the area a user cares about, styles mix whenever a model summary falls back to a raw feat(scope): title, and there is no Chinese version despite a large Chinese-speaking user base. UI changes also ship without visuals even when the pull request already carries Before/After screenshots. Measured on the last two stable releases, only about 4% of release pull requests carry body images, so screenshots are best-effort decoration while the themed bilingual digest is the structural improvement.

Reviewer Test Plan

How to verify

1. Unit suites (new and updated coverage for extraction, validation, bilingual rendering, fallbacks, and changelog embedding): npx vitest run --config ./scripts/tests/vitest.config.ts scripts/tests/generate-release-notes.test.js scripts/tests/generate-changelog.test.js scripts/tests/ai-release-notes-workflow.test.js. Expected: everything green except five pre-existing appendDegradedStepSummary failures that reproduce on unmodified main (verified in a temporary worktree).
2. No-model fallback regression: env -u OPENAI_API_KEY -u OPENAI_BASE_URL -u OPENAI_MODEL node scripts/generate-release-notes.js --repo=QwenLM/qwen-code --tag=v0.21.12 --previous-tag=v0.21.11 --target=v0.21.12 --dry-run. Expected: today's v1 layout, byte-identical to the same command on main (diffed).
3. Model-driven path (requires OPENAI_API_KEY / OPENAI_BASE_URL / OPENAI_MODEL): the same command with model env vars set. Expected: v2 marker, bilingual highlights, themed sections with intros, a 中文摘要 block, a collapsed appendix with normalized titles and author credits, and the Full Changelog trailer. Observed locally with qwen3.8-max: one summaries batch hit the 180s client timeout once and recovered on retry; one oversized summary degraded to its normalized title with a ::warning:: — both degradation paths exercised for real.
4. Changelog regression: node scripts/generate-changelog.js --dry-run — output is unchanged while all live releases are v1; the v2 transform is covered by the new unit test.

Evidence (Before & After)

Before (today, v0.21.12): ## Highlights followed by a ## Complete Change List wall of ~50 type-bucketed entries. After (dry-run of the v0.21.12..main range with qwen3.8-max):

## Highlights
- Deny-by-default guardrails for the qwen-autofix footprint gate... (#9156)
...
## Autofix guardrails
qwen-autofix now enforces a deny-by-default footprint check...
- autofix: deny-by-default footprint gate and positional window censuses ([#9156](...))
---
## 中文摘要
### 亮点
- qwen-autofix 默认启用基于白名单的足迹门禁... (#9156)
### Autofix 安全管控
qwen-autofix 现强制执行默认拒绝的足迹检查...
<details><summary>Complete Change List (2 pull requests)</summary>

#### Features
- autofix: deny-by-default footprint gate and positional window censuses ([#9156](...)) by @doudouOUC
...
</details>

Tested on

Environment (optional)

Node 22, scripts run directly with node, gh authenticated read-only against QwenLM/qwen-code; all runs were --dry-run (nothing published).

Risk & Scope

• Main risk or tradeoff: the digest depends on the release workflow's configured model answering three JSON calls; slower models can hit per-call timeouts. The existing retry/backoff, circuit breaker, and fallback ladder absorb this — worst case is today's v1 layout with ::warning:: annotations, never a failed release step.
• Not validated / out of scope: no workflow or package changes; nightly/preview notes unaffected; a full 50-PR-range model run was not forced locally because the local model's thinking mode stalled on some PR bodies (small-range E2E passed; CI's own model configuration owns production runs).
• Breaking changes / migration notes: none. All existing v1 releases keep rendering exactly as before in CHANGELOG.md; the v2 marker only appears starting with the first release finalized after this lands.

Linked Issues

N/A — maintainer-requested readability improvement.