[Abhishek-Mohan]

Which issue does this PR close?

Part of #7358. This PR moves contributor-guide/timezones.md over; the other pages stay open in that issue.

Rationale for this change

The style guide from #7151 rules out "runs natively", "the native path" and similar phrases (N1), and, in the contributor guide, allows "native" before a noun only when it names something under native/ or the JNI boundary (N3). timezones.md was one of the pages named in the #7151 review as still using them.

What changes are included in this PR?

One page, docs/source/contributor-guide/timezones.md, eight wording changes:

Before	After	Rule
feeds another native expression	feeds another Rust-implemented expression	N3
date_format runs natively only in UTC sessions	Comet uses to_char for date_format only in UTC sessions, unless spark.comet.expression.DateFormatClass.allowIncompatible=true	N1, P16
has no native spelling	has no spelling that Tz::from_str accepts	N3
compares the native version (getTzdataVersion)	compares the native library's IANA database version (getTzdataVersion)	N3
Two Spark settings are not handled natively	Comet does not handle two Spark settings	N1
the cases the native path cannot handle	the cases their Rust implementation cannot handle	N1
a native path gated on "the session is UTC"	a Rust fast path gated on "the session is UTC"	N1
Check that the expression ran natively	Check that the expression ran in Rust	N1

The date_format row also fixes a claim: CometDateFormat.convert uses to_char outside UTC when the expression's allowIncompatible config is set.

The last row says "in Rust" rather than "in the Comet pipeline" because the sentence contrasts the Rust implementation with codegen dispatch, which also stays in the Comet pipeline.

Uses the guide allows are unchanged: "native code", "native side", "native plan", "native kernel", "native scan", "native implementation", the JVM/native boundary, and expect_native (N2, N3, N6).

How are these changes tested?

Documentation only.

• Checked each changed claim against the code at the branch head: CometDateFormat and CometConf.getExprAllowIncompatConfigKey (spark/.../serde/datetime.scala, CometConf.scala), CometTimeZone.nativeId, and NativeBase.getTzdataVersion with its Rust side in native/core/src/lib.rs.
• prettier --check passes on the changed page.
• Built the docs with Sphinx (-n) at the base and at the head: 32 warnings on each, none new, none on this page.

AI assistance: written with Claude Opus 5.5 through OpenCode.