An inline code span, mention or document chip wider than its timeline line is clipped at the message's measured width. The hidden part can't be seen or scrolled to, and nothing shows that text is missing.

## Observed

On main `10f06d2` in a real Chromium render of the timeline, at timeline widths from 360px to 1100px, a message containing

``Run `bun apps/host/src/cli.ts backup 98d620b37665c43a /tmp/…/issue-triage-backup` now please.``

lays the code span (about 1,050px of monospace) out on a line of its own, and the text block's hidden overflow cuts it off at the bubble's content edge. This happens in human and agent bubbles. Before #168's fix, a user bubble also measured its height at the code's full width, while the browser drew it at the narrower bubble width.

The #168 fix keeps this clipping bounded: such a token is clipped to the block's measured width instead of painting past the bubble. It does not add a way to reveal the hidden text.

## Expected

Long unbreakable tokens stay readable without breaking timeline layout. Options include horizontal scrolling inside the token, wrapping long code at grapheme boundaries (Pretext supports `overflow-wrap: break-word` for normal text items), or a visible truncation with a way to show the full text.

Related: #168. Dogfooding: #5.