refactor(read_file): carry image base64 once in structuredContent

[edgarsskore]

The image read_file result duplicated the base64 in structuredContent as both content and imageData. Drop the imageData field and have the preview widget render from the single content field, halving the image structuredContent payload. No behavior change: the content[] image block (LLM vision) and the widget's data URI are both intact.

Summary by CodeRabbit

• Bug Fixes
  • Simplified file preview data handling so image previews now rely on a single content field.
  • Improved image preview validation to better detect missing or empty image data.
  • Kept preview output behavior the same while making image rendering more consistent.

[coderabbitai]

No actionable comments were generated in the recent review. 🎉

ℹ️ Recent review info

⚙️ Run configuration

Configuration used: defaults

Review profile: CHILL

Plan: Pro

Run ID: e4f54687-2358-4126-8a0d-8c0bc3c8a006

📥 Commits

Reviewing files that changed from the base of the PR and between cd4a80d and 26ef999.

📒 Files selected for processing (3)

• src/handlers/filesystem-handlers.ts
• src/types.ts
• src/ui/file-preview/src/file-type-handlers.ts

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📝 Walkthrough

Walkthrough

The PR consolidates file preview image payloads onto a single content field in shared types, the filesystem read handler, and the image preview renderer. The image preview UI now reads and validates that field when building the base64 data URL.

Changes

Unified file preview payload

Layer / File(s)	Summary
Shared payload contract src/types.ts, src/handlers/filesystem-handlers.ts	FilePreviewStructuredContent uses a single content field for preview data, and the image branch in handleReadFile emits that field for image bytes.
Image preview rendering src/ui/file-preview/src/file-type-handlers.ts	renderImageBody validates payload.content and uses it to construct the data:<mime>;base64,... image source.

Estimated code review effort

🎯 2 (Simple) | ⏱️ ~10 minutes

Possibly related PRs

• wonderwhy-er/DesktopCommanderMCP#339: Updates the same image preview payload flow by changing the shared structured content shape and the image preview reader.
• wonderwhy-er/DesktopCommanderMCP#472: Also consolidates image preview payload handling around structuredContent.content and updates the preview UI to consume it.
• wonderwhy-er/DesktopCommanderMCP#488: Touches the same handleReadFile image branch and related image content packaging in src/handlers/filesystem-handlers.ts.

Suggested labels

size:L

Poem

🐇 I hopped through bytes of image light,
One content field made everything right.
No extra fluff, just base64 gleam,
A tidy preview in a rabbit dream.
Ears up high, the pixels sing!

🚥 Pre-merge checks | ✅ 4 | ❌ 1

❌ Failed checks (1 warning)

Check name	Status	Explanation	Resolution
Docstring Coverage	⚠️ Warning	Docstring coverage is 50.00% which is insufficient. The required threshold is 80.00%.	Write docstrings for the functions missing them to satisfy the coverage threshold.

✅ Passed checks (4 passed)

Check name	Status	Explanation
Description Check	✅ Passed	Check skipped - CodeRabbit’s high-level summary is enabled.
Title check	✅ Passed	The title clearly reflects the main change: refactoring read_file to store image base64 once in structuredContent.
Linked Issues check	✅ Passed	Check skipped because no linked issues were found for this pull request.
Out of Scope Changes check	✅ Passed	Check skipped because no linked issues were found for this pull request.

✨ Finishing Touches

📝 Generate docstrings

• Create stacked PR
• Commit on current branch

🧪 Generate unit tests (beta)

• Create PR with unit tests
• Commit unit tests in branch refactor/dedup-image-base64

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