fix(ui): keep the timeline's total when filtering, drop empty diff lines, use --mono

[zz-plant]

This fixes the four defects that #3 found but left out of scope.

Changes

• Timeline count. Filtering reset the timeline's total to the filtered set. With one chip off the count read "10 of 10 events", and after None it read "0 of 0".
  • Cause: applyFilters() called timelineView.applyFilter(filtered), then updateAll(filtered), which called timelineView.setData(filtered) again.
  • Fix: the timeline now takes the full set only on load, and filters through applyFilter. The count reads "10 of 12" and "0 of 12".
• Empty lines in Wording changes. A newly added sentence has no "before", and a removed sentence has no "after". Each printed an empty − or + line: 2 of the sample data's 10 lines. Empty sides are no longer printed.
• Undefined font token. RevertClusterDisplay, DiffView and CertaintyTimeline used var(--font-mono), which is defined nowhere, so their labels fell back to the body face. They now use the stylesheet's --mono.
• Pre-commit hook. Biome ignores Markdown and YAML, and exits non-zero when every path it is given is ignored. So any commit that touched only a .md file failed the hook. Both lint-staged globs now pass --no-errors-on-unmatched, which is the same fix nextconsensus-site uses.

Checks

• bun run lint, tsc --noEmit, bun run test, bun run build and bun run assets:check all pass.

• The same Chromium script was run against main and against this branch at 1440×900:

  	main	this branch
  Count with one chip off	10 of 10	10 of 12
  Count after None	0 of 0	0 of 12
  Count after All	12 of 12	12 of 12
  Empty − / + lines	2	0
  Labels in the monospace stack	0	3

• The commit went through the fixed hook. Running lint-staged on a Markdown-only staged change now exits 0; on main it exits 1.

🤖 Generated with Claude Code

https://claude.ai/code/session_01EpGaiBuSk5nCSV2hKyD6PN

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