Feature request: Support multiple conversation export formats (.md, .html, .json)

Preflight Checklist

• [x] I have searched existing requests and this feature hasn't been requested yet
• [x] This is a single feature request (not multiple features)

Problem Statement

Feature Request

The /export command currently ignores file extensions and always outputs .txt files.

Current behavior:

• /export conversation.md → exports to conversation.txt
• /export conversation.json → exports to conversation.txt

Proposed Solution

Desired behavior:
Support exporting to different formats based on file extension:

• .md - Markdown (content is already markdown-formatted, just preserve it)
• .json - Structured JSON with messages, timestamps, tool calls
• .html - Rendered HTML for sharing/viewing in browser

Alternative Solutions

Workaround:
Currently requires manually renaming: mv conversation.txt conversation.md

This would be a small quality-of-life improvement since Claude's responses already use markdown formatting.

Priority

Medium - Would be very helpful

Feature Category

CLI commands and flags

Use Case Example

_No response_

Additional Context

_No response_