fix(coverage): a parse-error range can end one line past the end of the file

[CaptainMittens]

scripts/setup-windows.ps1 has 326 lines. Its parse-coverage report ends the last range at line 327, which does not exist:

113-113,113-113,245-327

Found while building the CI coverage gate in #1941; not fixed there.

What happens

The tree-sitter node for that region is start=(244,2) end=(326,0). An end column of 0 means the node stopped right after the previous line's newline, so it holds no text on the row it points at. cbm_error_regions_push adds 1 to that row to convert to 1-based, which names one line past the end of the file whenever a region runs to EOF.

Why it matters

A reader told to open line 327 of a 326-line file has been given advice that cannot be followed, in a report whose whole job is to say honestly which lines are missing. It also inflates the range's share of the file, which the coverage gate added in #1941 measures against a 25% threshold.

Suggested fix

Clamp the end to the row above when the end column is 0 and the node spans more than one row.

Related: #963, #1941. Sibling finding: the duplicated 113-113 range in the same string.