chore: remove small dead leftovers

[marius-kilocode]

Removes three pieces of dead code found during a cleanup pass. The diff is net negative (14 insertions, 52 deletions).

Changes

• Mermaid default labels: packages/ui/src/kilocode/mermaid/markdown-mermaid.ts had a hardcoded English labels object and a mergeLabels fallback. The only caller (packages/ui/src/components/markdown.tsx) always builds a complete MermaidLabels from i18n keys, so every default was shadowed. Removed the default and mergeLabels; renderMermaid now takes the caller's labels directly. renderMermaid is not exported from any public entry.
• Duplicate Mermaid story: packages/ui/src/kilocode/mermaid/markdown-mermaid.stories.tsx exported a Mermaid story that duplicates the MarkdownMermaid story in packages/kilo-vscode/webview-ui/src/stories/shared.stories.tsx, which the same Storybook loads. Removed only the duplicate export; MermaidError and MermaidThemes remain.
• Rename-only alias: packages/kilo-vscode/webview-ui/src/components/chat/background-agents.ts exported children as a pass-through to the private taskChildren. Exported taskChildren directly and updated the importers (ChatView.tsx, SubagentPanel.tsx, and the unit test) rather than keeping an alias.

No behavior change. No new helpers or tests.

Evidence

• bun run --cwd packages/kilo-vscode lint passes.
• bun test tests/unit/background-agents.test.ts from packages/kilo-vscode: 24 pass.
• bun test src/kilocode/mermaid from packages/ui: mermaid tests pass. The markdown-bidi.test.ts case fails on a pre-existing unbuilt @opencode-ai/core module, unrelated to this change.
• bun run --cwd packages/kilo-vscode typecheck and packages/ui typecheck report only pre-existing environment errors (unbuilt workspace packages and stale SDK in node_modules), none in touched files.

[kilo-code-bot]

Code Review Summary

Status: No Issues Found | Recommendation: Merge

Files Reviewed (6 files)

• packages/kilo-vscode/tests/unit/background-agents.test.ts
• packages/kilo-vscode/webview-ui/agent-manager/SubagentPanel.tsx
• packages/kilo-vscode/webview-ui/src/components/chat/ChatView.tsx
• packages/kilo-vscode/webview-ui/src/components/chat/background-agents.ts
• packages/ui/src/kilocode/mermaid/markdown-mermaid.stories.tsx
• packages/ui/src/kilocode/mermaid/markdown-mermaid.ts

Verified the removals are genuinely dead: renderMermaid's only caller (packages/ui/src/components/markdown.tsx:567) builds a complete MermaidLabels from i18n keys, the renamed taskChildren has all importers updated (no remaining children references from background-agents), and the dropped Storybook Mermaid story is not referenced by the visual-regression spec, which targets shared--markdown-mermaid. No changes touch shared upstream opencode files.

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_{Reviewed by deepseek-v4.1-flash · Input: 0 · Output: 0 · Cached: 0}

_{Review guidance: REVIEW.md from base branch main}