Fix agenda timer card to display hours correctly

[johnnycrich]

What is in this PR?

A minor UI fix to the meeting guide card for the display of an agenda item's remaining time, closing #367.

Changes in the codebase

In _MeetingGuideCardState:

• Increase the width of the container displaying the agenda item's time to accommodate longer time formats.
• Updated the logic for formatting the remaining time so that hours are shown if the time remaining is greater than zero hours.

Testing this PR

• Start a meeting and set an agenda section to a short time (e.g. 10 sec)
• Observe the timer counting down in min:sec.
• Stay in that section without "continuing" for more than 1 hour past time (sorry)
• Observe the timer counting down in hours:min:sec.

[Copilot]

Pull request overview

This PR updates the live meeting guide card timer display so agenda item remaining time can include an hours component when needed.

Changes:

• Expands the timer container width to fit longer time strings.
• Changes remaining-time formatting to conditionally show hours.

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[github-actions]

Visit the preview URL for this PR (updated for commit 183d2fd):

https://gen-hls-bkc-7627--pr435-367-meeting-section-cxqmlj6f.web.app

_{(expires Wed, 10 Jun 2026 18:02:15 GMT)}

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_{Sign: eed668cca81618d491d024574a8f8a6003deaa8d}

[katherineqian]

Hey @johnnycrich, thanks for this fix! Unfortunately I tested on the staging link and the behavior doesn't seem to be fixed -- see below screenshots:

1. An hour has almost passed!

2. Observe that the timer still rolls over, and the URL is the staging preview link.

[katherineqian]

Requested changes as in above comment.

[johnnycrich]

@katherineqian This should be all set!