fix: v0.15 审查修复 — 文件名冲突、版本锁定、文档补全、降级路径

审查 Codex v0.15 后修复以下问题：

1. agent.md → AGENT.md：消除 macOS 大小写不敏感文件系统上的文件名冲突
2. HANDOFF.md：validator 规则数从"6 条"更正为"R1-R9"
3. makelive 版本锁定到 0.7.0（live-photo-production.md + package-live-photo.py）
4. 补充 Swift metadata helper 脚本的执行说明和依赖要求
5. platform-specs.md：将"Observed support"改为"截至 2026-07 实测"
6. SKILL.md：补充 GIF/MP4 降级路径，覆盖无法走 iPhone/AirDrop 的发布场景

由 Kiro (Claude Code) 完成审查和修复。

Co-Authored-By: Claude <noreply@anthropic.com>

SKILL.md

@@ -311,6 +311,7 @@ Final response (after the user has reviewed or asked for auto-check) should incl
 - For any image fetched from the web: source URL + site + the attribution decision the user made.
 - For Live Photo: the `.pvt` package path, the debug `JPG + MOV` pair, target platform duration, and validation summary.
 - For Live Photo publishing: remind the user of two things: platform limits (`5s` Xiaohongshu, `3s` WeChat Official Account) and publish path (AirDrop the `.pvt` package as one item to iPhone, then publish from the matching mobile app path; desktop/web upload paths generally cannot recognize `.pvt` as a publishable Live Photo).
+- If the user cannot use the iPhone/AirDrop publishing path (e.g. desktop-only workflow, Android, or a platform that does not support Live Photo), offer a degraded delivery: export a short looping GIF or a silent MP4 clip from the same MOV source. The GIF/MP4 keeps the motion evidence but loses the Live Photo tap-to-play experience. Confirm with the user before switching to this fallback.
 - Any unresolved risks, such as source images being low resolution.
 
 ## Non-Negotiables