fix: parse HTTP headers from JSON string format

[hezhizhen]

Change Summary

Problem:
HTTP block headers were being lost during parsing. The frontend stores headers as a JSON string, but the backend only supported object format.

Solution:
Modified from_document to support both string and object formats.

Motivation and details

Any additional details about the changes you made, such as why you made them, what problems they solve, and how they work.

Tasks

• Regenerated TS-RS bindings (if any ts(export) structs have changed)
• Updated the documentation in docs/ (if any application behavior has changed)
• I am happy for maintainers to push small adjustments to this PR, to speed up the review cycle

[greptile-apps]

Greptile Overview

Greptile Summary

Fixed HTTP block header parsing to handle both JSON string format (from frontend) and object format (for backward compatibility).

• Added parsing logic to detect and handle headers as JSON strings
• Maintained backward compatibility with object format
• Added test coverage for string-format headers

Important Files Changed

File Analysis

Filename	Score	Overview
crates/atuin-desktop-runtime/src/blocks/http.rs	5/5	Fixed header parsing to support both JSON string and object formats from frontend

[greptile-apps]

_{1 file reviewed, no comments}

_{Edit Code Review Agent Settings | Greptile}

[ellie]

thank you! really appreciate the fix <3