fix(app): use resolved Shiki theme for code blocks

[taneja-garvit]

Fixes #2440

Summary

• use the resolved app theme for Shiki code highlighting instead of hardcoding github-light
• fix unreadable code blocks in dark mode
• update shared markdown/code rendering paths so code blocks refresh when theme changes

Fixes #2440

Test plan

• Switch to dark mode and render a code block in an assistant message
• Confirm syntax colors use the dark Shiki palette
• Switch back to light mode and confirm code blocks update correctly
• pnpm typecheck
• pnpm --filter @openwork/app exec bun test tests/theme.test.ts

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Project	Deployment	Actions	Updated (UTC)
openwork-landing	Ready	Preview, Comment, Open in v0	Jul 8, 2026 7:57pm

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[Pablosinyores]

Read through this and the approach is right. useSyncExternalStore(subscribeToTheme, getResolvedShikiTheme) is the correct primitive for pulling theme into render without a hand-rolled listener, and adding shikiTheme to the highlight effect deps in both MarkdownBlockInner and CodeBlockCode is what actually makes blocks re-highlight on toggle. The theme ?? resolvedTheme fallback in CodeBlockCode keeps explicit-theme callers working while defaulting everything else to the resolved app theme — clean.

One minor thing in markdown.tsx: the cached-HTML shortcut

const html = !streaming && highlightedHtml?.text === text ? highlightedHtml.html : syncHtml;

is keyed on text only, not on theme. On a light/dark toggle where the text is unchanged, highlightedHtml.text === text stays true, so the previously highlighted (old-theme) HTML shows until the effect's async re-highlight resolves and replaces highlightedHtml. It self-corrects because the effect now depends on shikiTheme, so it is a brief flash rather than a stuck state — just flagging in case you want to also gate that memo on theme to kill the transient. Not a blocker.

Mapping resolved light/dark to github-light/github-dark is exactly the right scope for #2440. Nice fix.

[taneja-garvit]

Good catch - makes sense, the memo should be theme-aware too so we don't even get the transient. Pushing a fix now to also gate highlightedHtml on shikiTheme

[taneja-garvit]

@Pablosinyores Pushed a small follow-up for this. I made the cached highlighted HTML theme-aware as well, so we don’t briefly reuse old-theme Shiki output during a light/dark toggle.