[browser] Fix WebAssembly publish output path message

[maraf]

Fixes #99292
Related change in SDK dotnet/sdk#55963

wasmbrowser publish currently reports the generic publish/ directory even though the servable application is under publish/wwwroot/. Add shared WebAssembly build and publish messages that identify the wwwroot output directory, while suppressing nested-publish duplicates.

The Wasm template tests assert the exact build and publish paths and require one occurrence per phase.

Expected console output:

Before:
app -> bin/Release/net8.0/publish/

After:
app -> bin/Release/net8.0/publish/
app (wwwroot) -> bin/Release/net8.0/publish/wwwroot/

The corresponding dotnet/sdk change should remove the obsolete Blazor 6.0 _BlazorCopyFilesToOutputDirectory output message so the shared target is the single source of truth. That change is outside this repository.

Validation: Mono/libraries baselines and browser-wasm package build succeeded. The focused WBT test assembly builds, but test execution is blocked in this environment by the local workload package-version check in eng/testing/workloads-browser.targets.

Note

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Pull request overview

This PR adjusts WebAssembly browser (wasmbrowser) build/publish logging so console output identifies the servable wwwroot directory (e.g., publish/wwwroot/) rather than only the generic publish/ path, and adds coverage to ensure the message appears exactly once per phase.

Changes:

• Add high-importance MSBuild messages for $(TargetDir)/wwwroot (build) and $(PublishDir)/wwwroot (publish), suppressed during nested publish.
• Add a Wasm template test that asserts the new (wwwroot) -> .../wwwroot/ message occurs exactly once in both build and publish output.

Reviewed changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated 1 comment.

File	Description
src/mono/wasm/Wasm.Build.Tests/Templates/WasmTemplateTests.cs	Adds a test asserting the (wwwroot) output-directory messages appear once for build and publish.
src/mono/nuget/Microsoft.NET.Sdk.WebAssembly.Pack/build/Microsoft.NET.Sdk.WebAssembly.Browser.targets	Emits new high-importance messages for build/publish wwwroot output directories, skipping nested publish.

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🔵 Needs a closer look

The new test and build-phase message appear to compute/output inconsistent path forms (absolute vs relative), making the assertions and console output behavior likely incorrect/brittle.

Review details

Suppressed comments (3)

Previously missed (2) — in code that hasn't changed since the last review.

src/mono/nuget/Microsoft.NET.Sdk.WebAssembly.Pack/build/Microsoft.NET.Sdk.WebAssembly.Browser.targets:980

• PublishDir is normalized from the relative $(OutputPath) in this targets file (so the publish message prints a relative bin/.../publish/wwwroot/), but the build message uses $(TargetDir) (typically rooted/full). That risks inconsistent output (absolute for build, relative for publish) and makes the message less likely to match what terminal logging and tests expect. Prefer basing the build message on $(OutputPath) for consistency with the publish path computation here.
  src/mono/wasm/Wasm.Build.Tests/Templates/WasmTemplateTests.cs:69
• The test builds the expected (wwwroot) output directories using projectDir, producing an absolute path. The WebAssembly SDK targets set PublishDir/OutputPath as relative (bin/...) paths, and the console output message is intended to show those relative paths; this assertion is likely to fail by mismatching absolute vs relative.

This issue also appears on line 73 of the same file.

src/mono/wasm/Wasm.Build.Tests/Templates/WasmTemplateTests.cs:77

• Same as build: the publish assertion currently expects an absolute .../bin/.../publish/wwwroot/ path, but PublishDir is defined as a relative bin/.../publish/ path in the imported targets. This makes the test brittle and likely incorrect for the actual console output.

            string publishOutputDirectory = Path.Combine(
                projectDir,
                "bin",
                config.ToString(),
                DefaultTargetFramework,

• Files reviewed: 2/2 changed files
• Comments generated: 0 new
• Review effort level: Lite