fix(typst): deduplicate cell-level line entries in hlines/vlines

[EinMaulwurf]

NOTE: This PR and the code changes are entirely "vibe coded" using GLM-5.2.

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typst_hlines() and typst_vlines() emitted fragmented chains of table.hline()/table.vline() segments covering the same span whenever @style_lines contained duplicate (i, j, line, color, width) tuples.

These duplicates arise routinely: theme_tinytable() adds style_tt(i = 0, line = "b", ...) and so does the user; the lazy style system records both calls and expands them to identical per-cell entries in @style_lines. typst_split_chunks() then saw phantom breaks in diff(x) != 1 and produced one chunk per duplicated j value.

Minimal repro before the fix:

tt(mtcars[1:5, 1:5]) |>
  style_tt(i = 0, line = "b", line_color = "black", line_width = 0.05) |>
  save_tt("typst")

emitted 6 fragmented table.hline(y: 1, ...) segments covering sub-ranges of [0, 5). After the fix, it emits a single
table.hline(y: 1, start: 0, end: 5, ...).

Also visible in test-typst.R's typst-issue592.typ snapshot, where the x:0 vline was previously split into 5 overlapping fragments (0-1, 0-2, 1-7, 6-12, 11-16). The snapshot is regenerated to reflect the correct single-segment output.

Fix: deduplicate identical rows of k inside the lapply() bodies of typst_hlines() and typst_vlines(), after the split() grouping. Other backends (html, latex/tabularray, markdown/grid) are unaffected — they either aggregate per cell (html) or build ranges that absorb duplicates (tabularray).

Tests:

• Regenerate inst/tinytest/_tinysnapshot/typst-issue592.typ
• Add regression tests in inst/tinytest/test-bugfix.R covering both "user re-declares theme line" and "user adds the same line twice"

[vincentarelbundock]

Does this maintain visible "gutters" between lines under spanning Colum headers?

[EinMaulwurf]

Yes it does:

x <- tt(mtcars[1:10, 1:8]) |>
  group_tt(j = list("Engine" = 1:4, "Trans" = 5:8)) |>
  group_tt(j = list("Cars" = 1:8))
cat(save_tt(x, "typst"))

[vincentarelbundock]

thanks, got a chance to check it out and it's a nice improvement. merged.