feat: add support for custom context files and direction

[abubakarsiddik31]

This PR introduces a major enhancement to the video generation pipeline: the ability to provide custom context and direction files. Creators can now steer the AI agents with specific angles, key facts, tone preferences, and constraints, ensuring the final output aligns perfectly with their vision.

🌟 Key Features

• CLI Support: Added a new -c, --context flag to the CLI.
  Reference any local Markdown or text file to inject detailed
  instructions into the generation process.
• Deep Pipeline Integration: Context is now systematically passed
  through the entire lifecycle:
  • Researcher: Focuses searches on specific angles or data
    points provided.
  • Creative Director: Adheres to the requested tone, hook
    styles, and narrative structure.
  • Critic: Evaluates the plan against the creator's specific
    constraints and gives feedback if they aren't met.
• API & Worker Support: The /api/v1/jobs endpoint now accepts a
  context string, enabling the same level of control for web-based
  or programmatic integrations.
• Private Briefing Workflow: Created a topics/ directory
  (automatically gitignored) where users can store their private
  project briefs.

🛠 Technical Changes

• CLI: Updated args.ts and index.ts to handle file reading and
  validation for context.
• Agents: Modified research.ts, creative-director.ts, and
  critic.ts to include optional context in system prompts.
• Server: Updated server.ts and worker.ts schemas to support the
  new context field (with a 5,000-character limit).
• Documentation: Added a comprehensive usage guide to the README
  and provided a topics/example.md template to help users get
  started.

📖 Usage Example

1 pnpm start "the apollo 13 disaster" --context topics/my-brief.md

Example Brief (topics/my-brief.md):

Focus on the emotional experience of the astronauts rather than
technical details.
Tone: Tense, then hopeful.
Must include: The CO2 scrubber improvisation.

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📝 Contributor Note
The topics/ folder is designed to keep your creative briefs local
and private while giving you full control over the AI's output.

[tsensei]

@claude review

[claude]

Claude Code is working…

I'll analyze this and get back to you.

View job run

[tsensei]

Closing in favor of #44 (landed as v0.18.0).

#44 covers the same need with a narrower design: direction only influences the Creative Director (not research/critic), uses free-form markdown parsed by the LLM, and adds score replay (--score) for reusing previous plans when downstream stages fail. Also includes web UI support, 10KB byte-limit validation, and 28 tests.