[kieronlanning]

Problem

The Release packages job failed on:

dotnet build src/ResourceKit.slnx --configuration Release --no-restore
aspire.hosting.apphost/13.6.4/build/Aspire.Hosting.AppHost.targets(433,5):
  error ASPIRE009: Example.AppHost is configured to use the Aspire CLI bundle,
  but the bundle could not be resolved...
  Automatic Aspire CLI bundle setup failed with exit code 1.

The PR run ten minutes earlier had passed that same Release build on the same sources.

Root cause

Both example AppHosts set AspireUseCliBundle=true, which makes a build require a resolvable
DCP/dashboard bundle. With none present, Aspire.Hosting.AppHost.targets runs
dnx aspire.cli@13.6.4 setup once per AppHost, so a single solution build restores and extracts the
same CLI concurrently. Reproduced on Linux with a fresh $HOME/.aspire:

CONCURRENT_A_EXIT=1
Unhandled exception: The process cannot access the file
  '.../aspire.cli/13.6.4/aspire.cli.13.6.4.nupkg' because it is being used by another process.
CONCURRENT_B_EXIT=0

Exit code 1, which MSBuild reports only as ASPIRE009. It is a race, which is why it passed some runs and
failed others. Neither shared pipeline can install the CLI before its own dotnet build
(purview-build.yml has no pre-build hook, and the release action is a composite action), so the build
must not need one.

Change

• Example.AppHost / Example.ManualAppHost now default AspireUseCliBundle to false (still
  overridable), the Aspire-documented fallback: the AppHost SDK adds
  Aspire.Dashboard.Sdk.<rid> and Aspire.Hosting.Orchestration.<rid> for the build machine's RID.
  Running the AppHosts is unchanged: the built assembly still carries dcpclipath /
  aspiredashboardpath metadata for 13.6.4.
• The resulting ASPIRE010 is suppressed only while the bundle stays off, and the opt-in remains:
  dotnet build -p:AspireUseCliBundle=true.
• New ExampleAppHostTests (Repository.UnitTests) fails if either project opts back in.
• AGENTS.md, docs/wiki/Contributing.md and CHANGELOG.md record the decision.

Verification (no aspire on PATH, empty Aspire home, the CI condition)

• dotnet build src/ResourceKit.slnx -c Release: succeeded, 0 warnings, 0 errors
• unit tier /*/*/*/*[Category=Unit]: 100 tests, 0 failed, 5 skipped
• dotnet csharpier check .: clean (107 files)

Closes the ASPIRE009 failure in https://github.com/purview-dev/aspire-resourcekit/actions/runs/42512003194