[VPEX] localenv: target a specific job task (--job-task <job-id>.<task-key>)

[rugpanov]

What

Replace the whole-job --job-id <id> flag with a task-scoped --job-task <job-id>.<task-key> (the task key is required).

Why

A single job can bind multiple tasks to different serverless environment versions (see the Workflows notebook-environments PRD). So a bare job ID is ambiguous — it can't resolve to one Python/serverless environment. Targeting a specific task removes the ambiguity: the CLI reads that task's environment directly.

This implements spec task D5 ([P0] CLI Changes.md, cli-spec-internal.md §2.2/§2.3/§4.3).

Behavior

• --job-task <job-id>.<task-key> resolves the named task. The value splits on the first dot, so task keys may themselves contain dots.
• Serverless task → version read directly from the environment it binds (environment_key → spec version). The job path no longer applies the serverless-vN default fallback — that now belongs solely to the bundle path. A task whose environment records no version is E_RESOLVE, not a guess.
• Classic task → resolved from its own new_cluster (or existing_cluster_id, via the Clusters API).
• Bare --job-task <job-id> (no task key) → E_USAGE, listing the job's task keys. Because listing requires a Jobs API call, this E_USAGE is emitted at the resolve phase; the error-code annotation in result.go is updated to note E_USAGE can also come from resolve for this case.
• Unknown task key → E_RESOLVE, also listing the available keys.

The ComputeClient seam gains JobTaskEnvironment (replacing GetJobSparkVersion) and a typed ErrTaskKeyRequired, so ResolveTarget can distinguish the missing-key usage error from a genuine resolve failure.

Tests

• job-classic-check / job-serverless-check now bind a task and resolve it.
• The old whole-job ambiguity cases (both-compute, multi-cluster mismatch, serverless-version mismatch) are obsolete under task scoping and are replaced by job-task-missing-key (E_USAGE), job-task-unknown (E_RESOLVE), and job-task-unpinned (E_RESOLVE, no fallback).
• serverless-default-check removed: the job path no longer defaults; the bundle default remains covered by TestResolveBundleServerless.
• Unit tests updated for the new interface + split/enumerate semantics. Build, unit, acceptance (localenv/help), lint, deadcode all pass.

Still Hidden; part of the pre-unhide hardening of environments setup-local.

This pull request and its description were written by Isaac.

[github-actions]

Approval status: pending

/acceptance/localenv/ - needs approval

31 files changed
Eligible: @rclarey, @anton-107, @misha-db

/cmd/environments/ - needs approval

Files: cmd/environments/compute.go, cmd/environments/sync.go
Eligible: @rclarey, @anton-107, @misha-db

/libs/localenv/ - needs approval

Files: libs/localenv/result.go, libs/localenv/target.go, libs/localenv/target_test.go
Eligible: @rclarey, @anton-107, @misha-db

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

[eng-dev-ecosystem-bot]

Integration test report

Commit: d0a7690

Run: 30025629102

	Env	💚​RECOVERED	🙈​SKIP	✅​pass	🙈​skip	Time
💚​	aws linux	4	4	322	1058	5:44
💚​	aws windows	4	4	324	1056	4:49
💚​	azure linux	4	4	322	1057	5:57
💚​	azure windows	4	4	324	1055	4:34
💚​	gcp linux	1	5	321	1059	5:18
💚​	gcp windows	1	5	323	1057	5:06

8 interesting tests: 4 RECOVERED, 4 SKIP

	Test Name	aws linux	aws windows	azure linux	azure windows	gcp linux	gcp windows
💚​	TestAccept	💚​R	💚​R	💚​R	💚​R	💚​R	💚​R
🙈​	TestAccept/bundle/invariant/no_drift	🙈​S	🙈​S	🙈​S	🙈​S	🙈​S	🙈​S
🙈​	TestAccept/bundle/resources/vector_search_endpoints/drift/recreated_same_name	🙈​S	🙈​S	🙈​S	🙈​S	🙈​S	🙈​S
🙈​	TestAccept/bundle/resources/vector_search_indexes/recreate/embedding_dimension	🙈​S	🙈​S	🙈​S	🙈​S	🙈​S	🙈​S
🙈​	TestAccept/ssh/connection	🙈​S	🙈​S	🙈​S	🙈​S	🙈​S	🙈​S
💚​	TestFetchRepositoryInfoAPI_FromRepo	💚​R	💚​R	💚​R	💚​R	🙈​S	🙈​S
💚​	TestFetchRepositoryInfoAPI_FromRepo/root	💚​R	💚​R	💚​R	💚​R
💚​	TestFetchRepositoryInfoAPI_FromRepo/subdir	💚​R	💚​R	💚​R	💚​R

Top 3 slowest tests (at least 2 minutes):

duration	env	testname
3:58	gcp windows	TestAccept
3:18	aws windows	TestAccept
3:14	azure windows	TestAccept