feat: introducing scenes workflow

[monsieurBoutte]

Overview

This branch adds a new generateScenes() workflow that uses Mux shot detection plus transcript cues to generate higher-level scene boundaries with titles.

What was changed

• Added src/workflows/scenes.ts, which implements scene generation, prompt customization, shot-window building/merging, AI output normalization, and error handling.
• Exported the new workflow from src/workflows/index.ts.
• Added scene examples in examples/scenes/basic-example.ts and examples/scenes/provider-comparison.ts, plus package.json scripts to run them.
• Added unit and integration coverage in tests/unit/scenes.test.ts and tests/integration/scenes.test.ts.
• Documented the new workflow and its prompt overrides in docs/API.md, docs/WORKFLOWS.md, docs/PROMPT-CUSTOMIZATION.md, and docs/EXAMPLES.md.

Suggested review order

1. src/workflows/scenes.ts
2. tests/unit/scenes.test.ts
3. tests/integration/scenes.test.ts
4. examples/scenes/basic-example.ts and examples/scenes/provider-comparison.ts
5. src/workflows/index.ts and package.json
6. docs/API.md, docs/WORKFLOWS.md, docs/PROMPT-CUSTOMIZATION.md, and docs/EXAMPLES.md

[snyk-io]

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