[air] Move AIR commands out of experimental

[caroline-db]

What did you change, and why?

• Move AIR commands and acceptance tests from their experimental locations into cmd/air and acceptance/air.
• Register databricks air as a top-level command and update help, ownership, and release notes.
• Keep a hidden databricks experimental air command that returns an error directing users to databricks air.
• Note that AIR commands remain under active development.
• This PR does not otherwise change AIR APIs, configuration formats, or workload behavior.

How do you know it works?

• Ran go test ./cmd/air ./cmd/experimental -count=1.
• Ran all AIR and root-help acceptance tests.
• Ran repository checks and Go lint with zero issues.

This PR was written with Codex.

[eng-dev-ecosystem-bot]

Integration test report

Commit: 2f9e93c

Run: 35607792521

	Env	✅​pass	🙈​skip	Time
✅​	aws linux	276	32	5:26
✅​	aws windows	278	30	4:42
✅​	azure linux	275	32	6:09
✅​	azure windows	277	30	4:42
✅​	gcp linux	276	32	6:53
✅​	gcp windows	278	30	4:04

Top 3 slowest tests (at least 2 minutes):

duration	env	testname
4:39	aws windows	TestAccept
3:51	azure windows	TestAccept
3:17	gcp windows	TestAccept

[github-actions]

Approval status: pending

/acceptance/experimental/air/ - needs approval

7 files changed
Suggested: @vinchenzo-db
Also eligible: @ben-hansen-db, @maggiewang-db, @apeforest, @bfontain, @panchalhp-db, @pardis-beikzadeh-db

General files (require maintainer)

181 files changed
Based on git history:

• @simonfaltum -- recent work in cmd/experimental/, .github/, cmd/

_{Any maintainer (@andrewnester, @anton-107, @denik, @pietern, @shreyas-goenka, @simonfaltum, @renaudhartert-db, @janniklasrose, @lennartkats-db, @rugpanov, @rclarey) can approve all areas.
See OWNERS for ownership rules.}