[air] Upload the finalized training config

[caroline-db]

What did you change, and why?

• Previously, command-line overrides and validation normalization were applied to the typed run configuration, but buildArtifacts reread the original YAML when creating training_config.yaml. The submitted workload used the overridden configuration while the uploaded artifact and air get still showed the original values.
• Keep an ordered, source-derived YAML representation through config loading, apply nested command-line overrides to it, and upload that final representation as training_config.yaml. The separately decoded configuration remains responsible for validation, normalization, and API submission.
• Preserve source key ordering and explicit empty or null values in the artifact. Reserialization does not preserve original comments or spacing.
• Add focused unit and acceptance coverage for nested overrides and uploaded artifact contents.

How do you know it works?

• go test ./experimental/air/cmd
• go test ./acceptance -run TestAccept/experimental/air/run-submit-overrides$ -tail -test.v
• ./task fmt-q
• ./task lint-q
• ./task checks
• ./task test
• Manually verified against a real workspace that air get displays the overridden nested value.

[eng-dev-ecosystem-bot]

Integration test report

Commit: 0d5d7b4

Run: 34626350787

	Env	💚​RECOVERED	✅​pass	🙈​skip	Time
💚​	aws linux	1	275	17	5:21
💚​	aws windows	1	277	15	3:34
💚​	azure linux	1	274	17	7:22
💚​	azure windows	1	276	15	5:04
💚​	gcp linux	1	275	17	6:42
💚​	gcp windows	1	277	15	5:33

	Test Name	aws linux	aws windows	azure linux	azure windows	gcp linux	gcp windows
💚​	TestAccept	💚​R	💚​R	💚​R	💚​R	💚​R	💚​R

Top 3 slowest tests (at least 2 minutes):

duration	env	testname
4:47	gcp windows	TestAccept
3:23	aws windows	TestAccept
3:14	azure windows	TestAccept

[github-actions]

Approval status: pending

/acceptance/experimental/air/ - needs approval

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

/experimental/air/ - needs approval

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

_{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.}