Redesign file link chips in agent replies so they read as links

[Yuruzuu]

File links in agent replies currently render as tinted, bordered chips (DataTemplate.luau · L76). In a reply that lists many files, the boxes stack up and the message reads as machine output rather than prose. Codex and Claude Code render the same references as plain links with a file icon, and those read better.

I tried three directions for file links in agent replies only (MarkdownFileLink). Each is one commit off main. All three use the same blue as other markdown links, keep the file-type icon, and split the line number from the file name so it can be styled separately. Click, menu, copy, tooltip and keyboard behavior are unchanged.

Screenshots are real ChatMarkdown renders, dark on the left and light on the right.

Before (main)

A. Link (design/file-link-a)

Medium weight, faded :76, and a dotted underline on hover, matching other markdown links. Closest to Codex.

B. Code reference (design/file-link-b)

Monospace with a dashed underline and :76. Gets a soft background on hover.

C. Prose (design/file-link-c)

Regular weight with a faint solid underline and line 76. The icon stays gray until hovered.

Scope and open questions

• Which direction? I lean A: it's consistent with every other link in a reply and the quietest in long file lists.
• Other chips: the same mention chip also appears for @file mentions in the composer and in sent user messages. Those are tokens you edit and delete as a unit, so I left them as chips. Should they change to match?
• Mobile: it draws its own version in the same three places. Once a direction is picked, I'll port it there so the clients match.

Explored with Claude Code (Claude Opus 5.5).