query --cwd ignores Windows verbatim prefixes and casing (list --cwd rules not shared)

[Drix10]

#51 added --cwd to query, but its path_under canonicalizes naively and
compares bytes, so on Windows a session recorded as \\?\C:\work\replay
never matches --cwd c:\WORK\replay. list --cwd already solved this
(#67: verbatim-strip, case-fold, lenient canonicalize); query just doesn't
share it.

How to reproduce

Session with cwd \\?\C:\work\replay, then
txcript query <term> --cwd c:\WORK\replay → 0 hits (same filter on list
finds it).

Proposed fix

Move the under_dir core to the lib crate (src/paths.rs) and route both
filters through it. Small, no behavior change otherwise.