Don't expand folded timelines just because users went to any anchor whatsoever

Summary:
Ref T12970. See PHI43. Currently, the "Show Older Comments" link gets auto-clicked if the user visits any anchor. This is not correct.

Instead, only auto-click it if the user visits a numeric anchor. This fixes the behavior approximately 98% of the time. See T12970 for a followup on the remaining ambiguous cases.

Test Plan:

• Viewed a revision with some folded transactions and a "Show Older Comments" link.
• Clicked a link to a file in the table of contents, with a hash like #1234abcd.
  • Before: Timeline expanded and I ended up somewhere bad.
  • After: Timeline no longer expanded.
• Manually changed hash to #1234 (purely numeric), saw timeline expand.

Reviewers: chad

Reviewed By: chad

Maniphest Tasks: T12970

Differential Revision: https://secure.phabricator.com/D18458