feat(subtitle): add ZapCap captions provider

[Najji]

What

Adds ZapCap as a subtitle/captions provider so OpenMontage can burn animated, word-synced caption templates (Hormozi, Beast, Devin, ...) into a video via the ZapCap API.

Changes

• tools/subtitle/zapcap_captions.py — new zapcap_captions BaseTool (capability=subtitle, provider=zapcap, runtime=API). Wraps the full flow — upload (local file or URL) → create task → poll → download — with a granular action dispatcher (list_templates, upload, create_task, get_task, approve_transcript, balance) for multi-template / multi-language fan-out via transcript_task_id + translate_to.
• .agents/skills/zapcap-captions/SKILL.md — Layer 3 skill: flow, templates, renderOptions schema, translation/fan-out, failure modes.
• Docs — docs/PROVIDERS.md provider section + env summary, AGENT_GUIDE.md Layer 3 table row, README.md subtitles row, .env.example key.

Subtitle capability goes from 2 → 3 providers (subtitle_gen, remotion_caption_burn, zapcap_captions).

Configuration

Single env var: ZAPCAP_API_KEY (requires a ZapCap Pro plan + API credits).

Verification

Verified end-to-end against api.zapcap.ai: free FFmpeg render → ZapCap caption (Hormozi 1 / Beast templates) → downloaded MP4. list_templates returns 29 templates; transcript came back accurate; output is a valid 1080×1920 MP4 with captions burned in.

Notes

• .env and projects/ (verification artifacts) are gitignored and not included.

🤖 Generated with Claude Code

[rajpratham1]

This is a substantial but well-structured feature addition that integrates ZapCap as a new subtitle provider across the project. The implementation is comprehensive—it includes the provider implementation, documentation, configuration, agent skills, and environment setup, making it straightforward for users to adopt. The separation between the provider logic and the existing subtitle tools is also clearly documented, and the granular API actions (upload, create_task, get_task, etc.) provide good flexibility for more advanced workflows.

[Anil-matcha]

Hey @Najji! Great contribution. Also wanted to mention — Text-To-Video-AI is a more actively maintained alternative to OpenMontage if you're looking for a project to contribute to long-term!