Add orthogonal setup-local flags (--no-constraints, --no-dbconnect, --no-provision) and a skipped phase status

[rugpanov]

Why

databricks environments setup-local had a single --constraints-only mode that
bundled "skip databricks-connect" together with the rest of the setup. A caller
that wants to write the project files but defer provisioning, or manage its own
dependency pins, had no way to express that. The setup steps are independent, so
the flags that control them should be too.

What

Three orthogonal, composable negative flags:

• --no-constraints — skip writing the remote Python-version and dependency
  pins (requires-python and the [tool.uv] constraint block). Existing values
  are left untouched, and (when provisioning) the resolved Python is still
  installed — the flag only governs what is written.
• --no-dbconnect — skip the databricks-connect dependency. Equivalent to
  the existing --constraints-only, which is left in place for now (either flag
  triggers the same behaviour).
• --no-provision — write the project files through the merge phase, then
  stop: no Python download, uv sync, or validation. Because it never invokes
  uv, its preflight no longer requires or installs uv either, so a files-only run
  works on a machine without uv.

A new skipped phase status (distinct from pending, which means an earlier
phase failed) is reported for the provision and validate phases under
--no-provision; venvPath is omitted and the --dry-run plan drops
wouldInstallPython. The text summary gains a dedicated "provisioning skipped"
variant so it no longer prints an empty venv path or a broken activation hint.

The --no-constraints "unmanaged" signal is a nil ConstraintDeps / empty
requires-python. parseConstraints now normalizes a missing
[tool.uv].constraint-dependencies to a non-nil empty slice, so nil uniquely
means the flag rather than an artifact that simply omits the section.

Note on --no-constraints + provisioning

--no-constraints governs only what is written. A provisioning run still installs
and validates the resolved Python, so if a user's kept requires-python is
disjoint from the target, uv surfaces it as a normal E_PROVISION rather than the
command guessing an alternative. The --no-constraints --no-provision pairing
skips provisioning entirely and avoids that tension.

Backward compatibility

Default runs (no new flags) produce byte-for-byte identical output and behaviour
— every existing acceptance golden is unchanged except the refreshed --help
listing. The --output json schemaVersion stays at 1: the new skipped
status only ever appears when one of the new flags is passed.

Testing

• Unit (libs/localenv): --no-provision writes files then skips
  provision/validate without invoking uv; --dry-run --no-provision marks them
  skipped and drops wouldInstallPython; --no-constraints leaves existing
  pins untouched and omits them greenfield; parseConstraints normalizes a
  missing constraint-dependencies; merge/render skip guards.
• Acceptance (acceptance/localenv): new no-provision (real run),
  no-constraints, no-dbconnect, no-provision-dry-run, and
  no-provision-text goldens, plus the refreshed help output.
• gofmt, go vet, and full go build ./... clean.

This pull request and its description were written by Isaac.

[github-actions]

Approval status: pending

/acceptance/localenv/ - needs approval

21 files changed
Suggested: @anton-107
Also eligible: @rclarey, @misha-db

/cmd/environments/ - needs approval

Files: cmd/environments/output.go, cmd/environments/sync.go
Suggested: @anton-107
Also eligible: @rclarey, @misha-db

/libs/localenv/ - needs approval

7 files changed
Suggested: @anton-107
Also eligible: @rclarey, @misha-db

General files (require maintainer)

Files: .nextchanges/cli/setup-local-orthogonal-flags.md
Based on git history:

• @janniklasrose -- recent work in .nextchanges/cli/

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