feat(zendesk): link every unflagged ticket on one digest line - #75

A ticket the model did not mark worth_looking_into was only counted in the header's category tally, then recorded as reported, so it never reached Discord as a link. #28891, a lost recovery phrase from 2026-10-08, went that way: the digest counted it under 🔑 and nobody saw it.

Those tickets now get one line under the abuse reports:

💤 **5** not flagged — 🔑 #28891, #28880 · ❓ #28870, #28866 · 💡 #28900

• Grouped by category, most common first, so the emoji says what each run of links is.
• Same link budget as the abuse-report line (COLLAPSED_LINKS_CHARS); past it the rest are counted as +N more, and the count always covers every ticket.
• Highlights beyond the display cap stay off it, so they still stay eligible for the next run.
• The line covers the tickets it counts, so a failed post leaves them eligible, the same as every other entry.

test_only_tickets_worth_looking_into_get_a_line asserted the old behaviour (one [# line in total) and now asserts that only flagged tickets get a line of their own. New TestUnflaggedLine covers placement, grouping, exclusions, coverage and clipping. Full suite: 832 tests pass.

https://claude.ai/code/session_019cnvrsCXsqLykDyQburD2f