fix(export): keep Windows auto off static layout first

[meiiie]

Description

Keep Windows auto Lightning exports on the streaming native/Breeze route instead of probing native static-layout before the stable path.

Motivation

Issue #581 reports 1.3.0 Windows 10 Lightning exports getting stuck at Prepare. The current Windows auto route probes native static-layout before Breeze/WebCodecs, which can hold the UI in the preparing phase before the stable streaming route gets a chance to run.

Type of Change

Bug fix / stabilization hotfix.

Related Issue(s)

Related to #581.

Changes Made

• Disabled the Windows auto static-layout-first policy behind an explicit constant.
• Limited native static-layout attempts to explicit Breeze or experimental NVIDIA CUDA opt-in.
• Added regression coverage proving default Windows auto starts the streaming native route first.
• Preserved NVIDIA CUDA opt-in behavior with a separate test that still allows static-layout-first when opted in.

Scope Note

This does not touch native helper binaries, CUDA source, packaged assets, timeline behavior, or the Windows 10 HUD/input issue. It addresses only the Lightning routing suspect from #581.

Testing Guide

1. On Windows, export a simple MP4 with Lightning / Auto.
2. Confirm the export leaves Preparing export... and either runs the streaming native path or falls back normally.
3. If NVIDIA CUDA opt-in is available and enabled, confirm that experimental static-layout routing still appears only through that explicit opt-in.

Checklist

• Focused hotfix branch from current origin/main
• Targeted tests updated
• Typecheck passed
• Scoped Biome passed
• No generated binaries included

Local Checks

• npm test -- src/lib/exporter/backendPolicy.test.ts src/lib/exporter/modernVideoExporter.fallback.test.ts
• npx tsc --noEmit --pretty false
• npx biome check --formatter-enabled=false src/lib/exporter/backendPolicy.ts src/lib/exporter/backendPolicy.test.ts src/lib/exporter/modernVideoExporter.ts src/lib/exporter/modernVideoExporter.fallback.test.ts
• git diff --check (exit 0; Git emitted local LF-to-CRLF warnings only)

Runtime/Repro Evidence

Not run in a packaged Windows build yet. This stays draft until Windows 10/11 packaged Lightning smoke confirms the route no longer stalls at Prepare.

Summary by CodeRabbit

• New Features

  • Added experimental NVIDIA CUDA acceleration support for video export

• Improvements

  • Refined Windows auto-export routing to prefer streaming-native exports by default
  • Clarified export route decision logic and fallback reason messages for more consistent behavior
  • Consolidated native-static eligibility and encoder-start decisions for predictable export flow

• Tests

  • Added and updated tests covering Windows auto routing, native-static vs streaming paths, and fallback behavior

[coderabbitai]

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• src/lib/exporter/modernVideoExporter.ts

---

📝 Walkthrough

Walkthrough

Windows "auto" backend preference now routes to streaming by default; a new feature flag disables native-static-layout priority for that case. ModernVideoExporter centralizes native-static-layout eligibility into a single flag combining Breeze preference or NVIDIA CUDA opt-in, and replaces scattered backend checks with this flag at both probe points. Tests verify Windows auto streams natively without static-layout steps and document CUDA-enabled static scenarios.

Changes

Backend Routing and Native-Static-Layout Gating

Layer / File(s)	Summary
Backend policy flag and route decision logic src/lib/exporter/backendPolicy.ts	WINDOWS_AUTO_STATIC_LAYOUT_FIRST_ENABLED flag gates native-static preference for Windows auto (disabled by default), and fallback reason string updates from "windows-native-static-fallback" to "native-static-layout-not-auto-default".
Route decision test expectations src/lib/exporter/backendPolicy.test.ts	Windows auto routing now expects breeze-stream selected and native-static-layout rejected, with shouldPreferNativeStaticLayoutBeforeBreeze("win32", "auto") returning false and updated route reason semantics.
Exporter native-static-layout eligibility centralization src/lib/exporter/modernVideoExporter.ts	New shouldTryNativeStaticLayout flag combines "breeze" preference with experimentalNvidiaCudaExport and prefersNativeStaticLayoutBeforeBreeze, updates shouldDeferNativeEncoderStart to align, and replaces backend-preference checks with the unified flag at both static-layout probe points.
Exporter test coverage for streaming and CUDA paths src/lib/exporter/modernVideoExporter.fallback.test.ts	New test verifies Windows auto native export takes streaming route (calls tryStartNativeVideoExport, skips static-layout, loads metadata once); existing Windows-auto static test updated to use experimentalNvidiaCudaExport: true flag.

Estimated code review effort

🎯 3 (Moderate) | ⏱️ ~20 minutes

Possibly related PRs

• webadderallorg/Recordly#562: Adds/propagates NVIDIA CUDA opt-in capability detection used as an alternate trigger for native-static-layout attempts.
• webadderallorg/Recordly#554: Previously changed Windows "auto"/Breeze/native-static route policy that this PR further adjusts.
• webadderallorg/Recordly#461: Modifies ModernVideoExporter export routing and native/Breeze probe points overlapping this PR's changes.

Suggested labels

Checked

Poem

🐰 Windows now prefers a streaming hop,
CUDA whispers where static pops,
One flag decides which path to chart,
Exports flow swift — a work of art. ✨

🚥 Pre-merge checks | ✅ 4 | ❌ 1

❌ Failed checks (1 warning)

Check name	Status	Explanation	Resolution
Docstring Coverage	⚠️ Warning	Docstring coverage is 0.00% which is insufficient. The required threshold is 80.00%.	Write docstrings for the functions missing them to satisfy the coverage threshold.

✅ Passed checks (4 passed)

Check name	Status	Explanation
Title check	✅ Passed	The title clearly and specifically summarizes the main change: disabling Windows auto routing away from static-layout-first to keep it on the streaming native route.
Description check	✅ Passed	The PR description comprehensively covers all template sections including clear description, motivation, type of change, related issues, changes made, testing guide, and a completed checklist.
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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• Create stacked PR
• Commit on current branch

🧪 Generate unit tests (beta)

• Create PR with unit tests
• Commit unit tests in branch fix/v130-lightning-auto-route-fallback

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[meiiie]

@coderabbitai review

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Actionable comments posted: 1

🤖 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.

Inline comments:
In `@src/lib/exporter/modernVideoExporter.ts`:
- Around line 385-391: The two flags are inconsistent: update the computation of
shouldTryNativeStaticLayout to include the same
shouldPreferNativeStaticLayoutBeforeBreeze(runtimePlatform, backendPreference)
check used by shouldDeferNativeEncoderStart so both follow the same conditions;
specifically, in the block where shouldTryNativeStaticLayout is set, add the OR
condition with shouldPreferNativeStaticLayoutBeforeBreeze(runtimePlatform,
backendPreference) (keeping the existing checks against backendPreference ===
"breeze" and this.config.experimentalNvidiaCudaExport === true) so both flags
remain aligned when the feature flag toggles.

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Fix all unresolved CodeRabbit comments on this PR:

• Push a commit to this branch (recommended)
• Create a new PR with the fixes

---

ℹ️ Review info

⚙️ Run configuration

Configuration used: Path: .coderabbit.yaml

Review profile: CHILL

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Run ID: 42ea93cf-38f1-4c82-8819-c3c5a8b74261

📥 Commits

Reviewing files that changed from the base of the PR and between 78594eb and 7ba7f70.

📒 Files selected for processing (4)

• src/lib/exporter/backendPolicy.test.ts
• src/lib/exporter/backendPolicy.ts
• src/lib/exporter/modernVideoExporter.fallback.test.ts
• src/lib/exporter/modernVideoExporter.ts