fix(mermaid): render flowchart sources missing the graph TD declaration

[passionjj]

Problem

Model-generated mermaid (e.g. from chat assistants) frequently omits the mandatory diagram-type declaration line - A[高帧率摄像头 120-240fps] --> B[...] with no leading graph TD. The kind whitelist in renderMermaid rejects such sources before rendering ever runs, so the mermaid node falls back to the raw-source error display even though the body is a perfectly valid flowchart.

Fix

• src/client/mermaid-safe.ts - new pure function ensureFlowchartKind(code): when the first token is not an already-declared graph/flowchart kind but the body contains flowchart edges (-->, ==>, -.->; negative lookahead keeps sequence -->> messages from matching), prepend graph TD. Everything else - declared kinds, sequence/gantt/pie bodies, plain text - passes through untouched: the diagram type is never guessed.
• src/client/mermaid-core.ts - renderMermaid wires it into the kind gate: undeclared flowchart bodies now render instead of throwing straight to the fallback; genuinely unclassifiable input still fails as before.
• src/client/mermaid-lazy.ts - re-export so the shared client bundle carries it.
• tests - 8 new cases in genui-mermaid-safe.spec.ts (21 -> 29, all green).
• lib artifacts - minimal rebuild (lib/assets/mermaid.js, lib/client.js, two .d.ts) so the published bundle carries the fix.

Verification

• jsdom end-to-end: an undeclared flowchart source renders to SVG; declared graphs unchanged; sequence-diagram bodies and plain text are still rejected (no type guessing).
• node --check passes on both bundles.
• Full suite: 296 passed / 104 skipped, no new failures (the 14 pre-existing failures are Windows-local environment items - install-script chmod / skill-md yaml version - reproduced identically on the pristine baseline).

Notes

• Changelog entry added under [Unreleased].

[taekchef]

@passionjj 感谢这个修复 🙏 方向和实现都很好:ensureFlowchartKind 只在「未声明类型 + 正文含流程图边」时补 graph TD,负向前瞻排除时序图 -->>,不做任何类型猜测——这正是模型输出降级的第一大来源,8 个新用例也覆盖得很全。我在本地完整跑了全量测试:310 passed / 104 skipped、0 失败。

CI 红的唯一原因是 Verify lib matches src 硬门:PR 里提交的 lib 产物是用与本仓 lockfile 不一致的工具链构建的,和 CI 重建结果有压缩变量名级别的漂移。由于 #40 已合入 main、lib/client.js 也有冲突,我顺手代劳了两件机械操作(已直接推到你的分支,commit 93c719a):

1. git merge origin/main(唯一冲突是构建产物 lib/client.js);
2. 用 pnpm install --frozen-lockfile + pnpm run build 重建并提交了 lib 产物,保证与 CI 重建逐字节一致。

CI 转绿后我就合并,感谢贡献 ✨