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

webroot/rsrc/js/application/transactions/behavior-show-older-transactions.js

@@ -17,6 +17,13 @@ JX.behavior('phabricator-show-older-transactions', function(config) {
     if (!hash) {
       return false;
     }
+
+    // If the hash isn't purely numeric, ignore it. Comments always have
+    // numeric hashes. See PHI43 and T12970.
+    if (!hash.match(/^\d+$/)) {
+      return false;
+    }
+
     var id = 'anchor-'+hash;
     try {
       JX.$(id);