chore(skills): merge similar changelog entries and credit external contributors

[wbxl2000]

Related Issue

N/A — agent-skill maintenance for the changelog workflow

Problem

The /pre-changelog and /sync-changelog skills produced release notes that read like a raw changeset dump:

• Many narrow fixes to the same UI surface were listed as separate bullets, making the `Bug Fixes` section a wall of similar entries.
• A web feature and the server/API changes that only backed it were both listed, even though users only perceive the web feature.
• SDK-only and provider/wire-format internals (capability mapping, XML markers, `getExperimentalFeatures()`) leaked into the CLI changelog.
• The `Thanks @user` credit was stripped for everyone, so external contributors were not credited.
• The `Polish` section mixed user-visible UX improvements with internal protocol adjustments without consistent ordering.

What changed

Updated three agent skills under `.agents/skills/`. No product code changed.

• `sync-changelog/SKILL.md`
  • New "Merge same-surface or same-kind fixes when you have three or more" rule so repetitive narrow fixes collapse into one higher-level entry; broad or genuinely distinct fixes stay standalone.
  • New "Contributor credit" rule: drop `Thanks ...!` for team members (`OWNER`/`MEMBER`/`COLLABORATOR`) but preserve it for external contributors (`CONTRIBUTOR`/`FIRST_TIME_CONTRIBUTOR`/`NONE`, or when unresolvable). Renders as `Thanks @user!` (EN) / `（感谢 @user）` (ZH).
  • Trim SDK-only and provider-internal detail from entries on both English and Chinese pages; keep the user-facing effect and required constraints.
  • Keep user-visible UX/performance improvements before protocol/internal adjustments within `Polish`; default-behavior changes usually classify as `Polish`.
  • Encourage a parallel sentence rhythm within a section on the Chinese page.
• `pre-changelog/SKILL.md`: step 3 now mirrors the merge / deduplicate / thanks / trim / ordering rules above so the preview matches the real sync.
• `gen-changesets/SKILL.md`: soften the "always split web + server API" guidance so a web feature whose server API is pure plumbing produces a single `web:` changeset, with a separate API changeset only when the API has independent user value.

This is skill-only guidance and does not enter any package output, so no changeset is needed (per Core Rule 5 of `gen-changesets`).

Checklist

• I have read the CONTRIBUTING document.
• I have linked a related issue, or explained the problem above.
• I have added tests that prove my feature works. (N/A — agent-skill docs only)
• Ran `gen-changesets` skill, or this PR needs no changeset. (No changeset — skill-only change, not in any package output)
• Ran `gen-docs` skill, or this PR needs no doc update. (No user-facing product behavior change)

[changeset-bot]

⚠️ No Changeset found

Latest commit: 3517b4a

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