Canonical .NET tool commands suppress native discovery and update failures

Peer-review finding

Reviewed snapshot: 5c38677469756c69f86678c0b907d82e15d0a539.
The parent independently replayed this finding using only synthetic fixtures and
harmless native children. No actual package operation or credential access was
performed, and no repository source was changed.

Severity: medium. Confidence: 10/10.
Existing labels: bug, module:dotnet, module:utilities.

Source at the reviewed commit:
modules\Shmuelie.DotNet\DotNetHelpers.ps1:30-45,88-104.
Forwarding entry points:
modules\Shmuelie.Utilities\DotNetHelpers.ps1:59-72,111-124.
The aggregate separately compensates in
modules\Shmuelie.PackageManagement\DotNetPackageProvider.ps1:1-22.

Cause and reachable impact: the canonical list command discards stderr and
never checks the native exit code; the update command moves diagnostics to
verbose output, parses them as if the invocation completed, and emits an
ordinary DotNetToolUpdateResult without checking native success. With
PSNativeCommandUseErrorActionPreference = $false (the normal opt-in native
error setting), even -ErrorAction Stop cannot make these failures visible as
PowerShell errors. Scripts can interpret a failed inventory as no installed
tools or a failed update as an unchanged tool and continue subsequent work.
Both lazy compatibility wrappers faithfully inherit the defect; this is not a
wrapper forwarding defect. The aggregate's explicit exit-code guard protects
its own path, so do not file this as a broken aggregate failure boundary.

Safe reproduction: the .NET cases in Repro-Candidates.ps1. The source
module's dotnet function is replaced by a fake that launches only fresh
pwsh -NoProfile -NonInteractive children emitting fixed synthetic text and
exiting 7. No SDK or tool command is run.

For both canonical and Utilities update commands, with -ErrorAction Stop:

{"ExitCode":7,"ErrorCount":0,"Caught":null,
 "Result":{"PackageId":"example.tool","Version":null,"Updated":false}}

For both listing commands, exit 7 yields zero errors and an empty collection.
Expected: native failure must produce a meaningful PowerShell error; an update
failure must not emit the normal result as though its outcome was determined.

Acceptance criteria:

• Check native completion explicitly for canonical discovery and update,
  independent of caller native-error preference; retain diagnostics and exit
  status in the reported error.
• Ensure -ErrorAction Stop stops the operation, ordinary error handling remains
  usable, and failed discovery is not silently treated as known empty inventory.
• Preserve successful result shapes, confirmation, scope, and streaming;
  Utilities wrappers must preserve the canonical errors without duplicate prompts.
• Add harmless-native-child tests for both canonical commands and wrappers, plus
  successful empty inventory, unchanged update, and aggregate fail-fast controls.

Tracking context: #186 intentionally preserved the old implementations during
migration; this is pre-existing behavior, not a newly introduced migration
regression. Existing adapter tests explicitly detect the hidden canonical
failure. Open #259 concerns independent DSC wrappers, not these canonical
commands. No matching open canonical issue was found. The behavior may warrant
an upstream-parity issue in the bash port if that port shares this native-error
handling; the parent should check its current implementation/issue inventory.

Read modules\Shmuelie.DotNet\DotNetHelpers.ps1 and its forwarding entries in modules\Shmuelie.Utilities\DotNetHelpers.ps1, then run the .NET cases in Repro-Candidates.ps1. Compare canonical, wrapper, and aggregate behavior against the acceptance criteria; done means native failures are reported and stopped, while successful result shapes and fail-fast controls remain covered by harmless-child tests.