fix: correct documentation inaccuracies in API and troubleshooting guides

[Copilot]

Addresses review feedback on PR #99 by fixing incorrect tool names, missing required fields, and invalid JSON syntax in documentation.

Changes:

• docs/troubleshooting.md: Replaced non-existent render_video tool with actual export_project tool name; removed reference to fictional "Tool execution timed out" error message; clarified timeout guidance to focus on system resources and deployment configuration

• docs/api.md: Added missing required effects: [] field to Project JSON clip example to match Clip interface in @ai-video-editor/shared-types

• docs/api.md: Changed code fences from json to jsonc for examples containing inline comments to prevent invalid JSON that breaks copy/paste

• docs/api.md: Documented optional model and projectData fields in copilot.message WebSocket payload (fields already supported by backend handler but previously undocumented)

Example:

{
  "type": "copilot.message",
  "payload": {
    "content": "Add a 5 second clip...",
    "projectId": "550e8400-e29b-41d4-a716-446655440000",
    "model": "gpt-4o-mini",      // optional: override model
    "projectData": { ... }        // optional: project snapshot for context
  }
}

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