Add parameter pills to tool placards in chat UI
Display key parameters (facet, day, topic) as compact pills on tool
call cards so users can see at a glance what filters/context the agent
used. Dates are formatted from YYYYMMDD to M/D for readability.
Also consolidates three duplicate date formatting implementations into
a single shared formatDay() helper.
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Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>