# Final structure cleanup — 2026-09-12

## Intent

Finish the structural cleanup after the component pruning pass without changing Mandelbrot numerical behavior. The production HTML is now the single source of truth for both release and regression.

## Changes

### Single source of truth

- Removed the persistent `tests/index.test.html` copy.
- `tests/regression.mjs` now parses and executes production `index.html` directly.
- `tests/browser_smoke.mjs` generates a temporary instrumented page from production `index.html`, then removes it even when browser connection fails.
- Added a regression assertion that a persistent test HTML copy must not reappear.

### Correctness fixes found during cleanup

- Fixed `cancelRender()` export cancellation/generation update. The production-only typo `truestate.token++` is gone; export cancellation and `state.token++` are separate operations.
- Fixed the render cancellation/error path that called the nonexistent `returnfinishRenderClock(...)` token. Cancelled generations now close the render clock correctly and return.

### Removed write-only state and UI churn

Removed production state that had no readers:

- `lastEngine`
- `frontierRounds`
- `frontierPixels`
- `frontierEscaped`
- `frontierIter`
- `frontierMinimumIter`
- `frontierConverged`
- `gpuUnavailable`
- `qualityIter`
- `refineMs`
- `lastRender`
- `gpuStage`

Progress-only `lastEngine` assignments and their no-op `updateStats()` calls were removed. The user-visible status continues to derive from `drawState`, unresolved counts, temporal fill, render clock, and GPU error state.

### Renderer diagnostics

Removed retained diagnostics that were never consumed:

- `this.adapter`
- `this.adapterInfo`
- `this.compilation`
- `this.uncapturedErrors`

Shader compilation errors are still checked and thrown immediately. The latest uncaptured GPU error is still copied to `state.gpuError`. Device-loss stage tracking stays in renderer-local `activeGpuStage` / `lastCompletedGpuStage`.

### Fixed-point / WGSL dead definitions

- Removed production-only unused `fromDec()` and `decimalRequiredBits()` helpers. Test decimal conversion now lives only in the test harness.
- Removed unused WGSL `FIELD_INTERIOR_LIKELY`.
- All 19 surviving kernels are byte-identical to the pre-cleanup kernels after deleting that single unused constant line.
- Simplified stale reference-selector comments and redundant return logic.

### Export metadata

Both export paths now call one `buildExportMetadata()` function. Common fields now have one definition for:

- finite-budget completion
- membership certification
- precision policy
- iteration policy
- view coordinates
- palette description
- renderer/shader version
- pixel contract

Path-specific tile/ring fields are added only when applicable.

### Small dead-code cleanup

- Removed dead `dispatchWork` local after correction accounting was deleted.
- Removed dead `sampleCount`, `lastUi`, and final-frame `elapsed` locals.
- Renamed stale `reusePreview` to `reusePriorField` and the no-frame `PREVIEW` draw-state label to `PENDING`.

## Verification

`node tests/regression.mjs` passes and directly executes production JS. It covers routing, finite-budget semantics, staged operation-limit scoring, exact interior proof, integer-grid history reuse, nearby reference reuse, Worker lifecycle, correction pipeline count, export cancellation/generation behavior, common export metadata, pinned WGSL hashes, and CPU worker smoke tests.

The optional browser smoke script passes syntax validation. A real WebGPU browser run is not claimed in this environment.