Add error handling for dagre layout and fallback to simple layout

[cxzl25]

Failed to layout SQL flow: Cannot set properties of undefined (setting 'order')

https://github.com/dagrejs/dagre/issues/234

[Copilot]

Pull request overview

This PR improves resilience of the SQL flow graph layout by handling Dagre compound-layout failures and falling back to a simpler layout, preventing the UI from hard-failing on known Dagre compound graph edge cases.

Changes:

• Wrap compound dagre.layout(g) in try/catch inside the staged (compound) layout path.
• On failure, log a warning and fall back to the existing “simple” (non-compound) Dagre layout.

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[Copilot]

The fallback layout is cached under cacheKey + "-fallback", but getLayoutedElementsWithStages (and SqlElementsToLayout) look up layoutCache using the original cacheKey. If dagre compound layout keeps failing for a given graph, this will re-run the failing layout and emit console.warn on every call (performance + log spam) instead of reusing the fallback.

Consider caching the fallback result under the original cacheKey (e.g., compute fallback once, layoutCache.set(cacheKey, fallbackResult), then return it), and/or avoid the -fallback suffix so subsequent calls immediately reuse the fallback without retrying the broken compound layout.

Suggested change

	return getLayoutedElements(flowNodes, flowEdges, cacheKey + "-fallback");
	return getLayoutedElements(flowNodes, flowEdges, cacheKey);

[minskya]

@cxzl25 where and how this change was required? I'd like to understand better the scenario. Thanks

[cxzl25]

where and how this change was required? I'd like to understand better the scenario.

When I open some complex SQL, it reports this error. This SQL has 5,000 lines and 350,000 characters.