fix: sync syntax highlighters with std lib

[prql-bot]

The nightly survey reviewed the two syntax-highlighting definitions and found they had drifted from the std lib (prqlc/prqlc/src/semantic/std.prql) and from each other:

• grammars/KSyntaxHighlighting/prql.xml — the date_functions list only contained to_text, missing the other three functions the date module exports: now, diff, trunc (std.prql L230-233). The types list also carried int128, which is not a PRQL type — std.prql defines no int128, and the type-system spec's sized-int roadmap stops at int64 (web/book/src/reference/spec/type-system.md). It was also absent from the highlight-prql.js sibling list, so removing it realigns the two highlighters.
• web/book/highlight-prql.js — DATATYPES listed timestamp but not its siblings date and time, although all three are type primitives defined together in std.prql (L45-47).

These are documentation/grammar definition files with no unit-test harness in the repo (the book just loads highlight-prql.js via book.toml), so no regression test accompanies the change — consistent with prior grammar fixes such as #5957.

[max-sixty]

The edits here check out against std.prql: the date module is exactly now, to_text, diff, trunc; int128 isn't a PRQL type; and date/time/timestamp are all primitives. CI is green.

One gap, though. web/book/highlight-prql.js has a header comment to keep it consistent with web/website/themes/prql-theme/static/plugins/highlight/prql.js, and the two DATATYPES lists were identical before this PR. Adding date/time to the book file but not the website file makes them diverge, and no CI check guards that pairing. The website highlighter is also still missing date/time relative to std.prql.

Adding date/time to web/website/themes/prql-theme/static/plugins/highlight/prql.js would complete the sync and keep both files aligned.

This was written by Claude Code on behalf of max

[prql-bot]

Good catch — added date/time to web/website/themes/prql-theme/static/plugins/highlight/prql.js in 5d6fe4c so its DATATYPES list matches the book file again. The two lists are now identical, and both are aligned with the primitives in std.prql.