* perf: cache KaTeX module import as singleton across all renderer instances
KatexRenderer.svelte dynamically imports katex, mhchem, and the CSS on every component mount. When a message contains multiple math expressions, this triggers redundant module resolution for each one. Move the import promise to a module-level singleton using Svelte's context='module' script block so it loads once and is shared across all KatexRenderer instances.
* Update KatexRenderer.svelte
ResponseMessage compared the entire message object via JSON.stringify on every reactive tick to detect changes. During streaming, content changes on every token, making the two O(content_length) JSON.stringify calls always return different results — pure wasted work. Add a fast O(1) comparison on content and done fields first. When either differs (the common streaming case), skip straight to cloning. Only fall through to the expensive JSON.stringify comparison for infrequent changes like sources, annotations, or status updates.
Add optional chaining to file.url.startsWith() calls to safely handle cases where file.url is undefined, preventing 'can't access property startsWith' TypeError in user messages with file attachments.
Fixes#19742 where file attachment containers did not inherit the chat direction setting, causing layout issues when typing in RTL languages like Persian.
Added dir={$settings?.chatDirection ?? 'auto'} to file container divs in:
- MessageInput.svelte (chat input file attachments)
- UserMessage.svelte (user message file display)
- ResponseMessage.svelte (response message file display)
- channel/Messages/Message.svelte (channel message file display)
The fix ensures file containers automatically detect and respect RTL text direction, maintaining proper layout alignment for RTL languages while preserving LTR behavior for Latin text.
