perf(web): filter codemirror chunk out of <modulepreload>

[naorsabag]

Re-ran Lighthouse after #114 deployed — Performance barely moved (mobile 42 → 41, desktop 89 → 84), even though the chunk split looked correct. Inspecting the deployed `index.html` showed why:

```html

\`\`\`

Vite/rolldown was eagerly emitting `modulepreload` for every named chunk, including the lazy codemirror one. Browsers happily fetched, parsed, and prepared CodeMirror on first paint anyway — exactly what the React.lazy on FlowEditorModal was supposed to prevent.

Fix: `build.modulePreload.resolveDependencies` strips the codemirror chunk from the preload list. The chunk still ships and still loads when FlowEditorModal's dynamic import runs (on "+ New flow" / Edit click), just not before then.

What's preloaded after this PR

Before:
```
rolldown-runtime, codemirror, flow, yaml, react
```

After:
```
rolldown-runtime, flow, yaml, react
```

That's ~140 KB gz off the first-paint network + parse budget.

SEO win from #114 stands

SEO went from 91 → 100 already; this PR doesn't touch it.

🤖 Generated with Claude Code

Summary by CodeRabbit

• Performance
  • Optimized the code editor component loading to reduce initial page load time by deferring non-critical resources until they are actually needed.

[coderabbitai]

Walkthrough

This PR modifies the Vite build configuration to add a build.modulePreload.resolveDependencies hook that filters out modulepreload links for CodeMirror chunks, ensuring they are only fetched when dynamically imported rather than eagerly preloaded at startup.

Changes

CodeMirror Lazy Loading Configuration

Layer / File(s)	Summary
Build modulepreload configuration packages/web/vite.config.ts	The build.modulePreload.resolveDependencies hook removes CodeMirror chunk preloads from the dependency list to prevent eager preloading of lazy-imported modules.

Estimated code review effort

🎯 1 (Trivial) | ⏱️ ~3 minutes

Possibly related PRs

• naorsabag/openhop#114: Both PRs handle CodeMirror code splitting; this PR filters modulepreload while the related PR adds manual chunk splitting for the codemirror module.

🚥 Pre-merge checks | ✅ 5

✅ Passed checks (5 passed)

Check name	Status	Explanation
Description Check	✅ Passed	Check skipped - CodeRabbit’s high-level summary is enabled.
Title check	✅ Passed	The title accurately summarizes the main change: filtering the CodeMirror chunk from modulepreload links in the Vite configuration for performance optimization.
Docstring Coverage	✅ Passed	No functions found in the changed files to evaluate docstring coverage. Skipping docstring coverage check.
Linked Issues check	✅ Passed	Check skipped because no linked issues were found for this pull request.
Out of Scope Changes check	✅ Passed	Check skipped because no linked issues were found for this pull request.

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✨ Finishing Touches

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• Create PR with unit tests
• Commit unit tests in branch perf/filter-codemirror-preload

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[coderabbitai]

🧹 Nitpick comments (1)

packages/web/vite.config.ts (1)

42-44: ⚡ Quick win

Scope this filter to HTML preloads only.

At Line 42, the filter is unconditional and will remove codemirror dependency preloads for both HTML and dynamic JS imports. This can add a waterfall when opening the editor. Restrict the filter to HTML host preloads using the context.hostType parameter, which preserves lazy-load responsiveness for dynamic imports while keeping first-paint optimizations.

♻️ Proposed patch

-      resolveDependencies(_filename, deps) {
-        return deps.filter((d) => !/\/codemirror-[A-Za-z0-9_-]+\.js$/.test(d))
+      resolveDependencies(_filename, deps, context) {
+        if (context.hostType !== 'html') return deps
+        return deps.filter((d) => !/(?:^|\/)codemirror-[A-Za-z0-9_-]+\.js$/.test(d))
       },

🤖 Prompt for AI Agents

Verify each finding against current code. Fix only still-valid issues, skip the
rest with a brief reason, keep changes minimal, and validate.

In `@packages/web/vite.config.ts` around lines 42 - 44, The unconditional filter
in resolveDependencies removes codemirror preloads for all host types; change
resolveDependencies(_filename, deps, context) to only filter when
context?.hostType === 'html' so HTML preloads drop codemirror-*.js but
dynamic/js imports keep those deps for lazy loading; specifically update the
resolveDependencies function to check context.hostType and return deps unchanged
for non-'html' hosts and apply the existing regex filter only for HTML hostType.

🤖 Prompt for all review comments with AI agents

Verify each finding against current code. Fix only still-valid issues, skip the
rest with a brief reason, keep changes minimal, and validate.

Nitpick comments:
In `@packages/web/vite.config.ts`:
- Around line 42-44: The unconditional filter in resolveDependencies removes
codemirror preloads for all host types; change resolveDependencies(_filename,
deps, context) to only filter when context?.hostType === 'html' so HTML preloads
drop codemirror-*.js but dynamic/js imports keep those deps for lazy loading;
specifically update the resolveDependencies function to check context.hostType
and return deps unchanged for non-'html' hosts and apply the existing regex
filter only for HTML hostType.

---

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📥 Commits

Reviewing files that changed from the base of the PR and between e3f9236 and b69f4d3.

📒 Files selected for processing (1)

• packages/web/vite.config.ts