fix(audit): the day dividers stand out: primary text on a raised band (#5214)

The operator, reviewing the audit log: "the dividers are good but should
stick out more maybe make the text color different". Column headers are
muted text on the card; a divider is now the primary text on the hover
surface, ruled above and below. The accent stays off it: the design system
keeps it off chrome, and Steward's amber sits near its warning colour.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

steward/static/steward.css

@@ -228,8 +228,11 @@ strong, b, th { font-weight: 500; }
 /* An audit entry's details, one fact a line (milestone 490). */
 .audit-facts { font-size: 0.8rem; color: var(--text-muted); }
 /* A divider row naming the group the rows under it fall in (Today, Older). */
-.table tr.table-divider th { padding: 1rem 1rem 0.4rem; background: var(--bg-card); border-bottom: 1px solid var(--border-mid); }
-.table tbody tr.table-divider:hover th { background: var(--bg-card); }
+/* A day group's divider reads above its rows: the primary text on a raised
+   band, where column headers are muted on the card (#5214). Not the accent:
+   that stays off chrome, and Steward's amber sits near its warning. */
+.table tr.table-divider th { padding: 0.55rem 1rem; color: var(--text); background: var(--bg-elevated); border-top: 1px solid var(--border-mid); border-bottom: 1px solid var(--border-mid); }
+.table tbody tr.table-divider:hover th { background: var(--bg-elevated); }
 .cell-note { font-size: 0.78rem; color: var(--text-muted); margin-top: 0.2rem; }
 /* An alert episode's own transitions, folded under it (#5316). */
 .episode-steps { margin-top: 0.3rem; font-size: 0.8rem; }