activity: group work items by goal and tag each with its kind

[creedants]

The agent activity page now groups work items by goal and tags each with its kind.

• The HTML page groups the unfinished items in its work-item strip under each goal's name, with one count line per group.
• The text form groups the items it lists, including finished ones, the same way.
• A kind tag is one of feature, fix, polish, upkeep, or study. Any other value shows no tag.
• Items with no goal share an Unassigned group, last.
• A store with no kinds and no goals gives the same page as before, byte for byte.
• The goal name is the only goal text shown, and it passes through the same privacy filter as every other line.

Known limits. The two forms can group different slices of the same store, because the strip shows unfinished items and the text form also lists finished ones. A malformed row in the goals table stops the page with a one-line message, as the other tables do. With many groups and very wide goal names the HTML page can run past its height frame; nothing is dropped without a note.

Reviewed at 102cdcc7.