///|
/// Render the self-contained AI Trace Clinic.
///
/// The page intentionally has no framework, server, or external asset. Its
/// default evidence mirrors `fixtures/agent-traces`: a selection-sort trace
/// whose stale-index swap first diverges at step 10.
pub fn render_trace_playground() -> String raise TraceError {
  // Preserve the established fallible API while validating the empty clinic
  // shell with the same scene rules used by imported traces.
  ignore(Scene::new(objects=[]))
  (
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    #|FrontierLab AI Trace Clinic
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Semantic Time-Travel Debugger · Schema v1
AI Trace Clinic
Turn an opaque wrong trace into a contract failure, the first divergence, two precise state comparisons, and a portable focused counterexample slice — in one click, fully offline.

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Find the first wrong step
Ready: the built-in incorrect example is loaded.

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Schema
Not run
Contract
Not run
First divergence
Not run
Focus
Not run

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Expected event vs actual event
✓ Expected
Run diagnosis.
✕ Actual
Run diagnosis.
Focused counterexample slice
Run diagnosis.

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State evidence
Actual transition into focus
Run diagnosis.
Reference vs actual at focus
Run diagnosis.

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Faulty selection sort - stale index
Run diagnosis to jump to the first bad step.

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Advanced details
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Drop a JSON file here or choose one 

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Semantic breakpoints

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Trace contract

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First divergence

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Quality diagnostics
    Windowed timeline
    At most 101 nearby entries are rendered for large traces.
    
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  )
}