Add a Copilot skill for investigating Azure DevOps pipeline build
failures. Given a build URL, it fetches run details, identifies failed
jobs/tasks via the timeline API, downloads .binlog artifacts, and
analyzes them with binlogtool to find root causes.

Example usage:

    ❯ what are the errors here: #10881

    ◐ The user is asking about errors in a GitHub PR. This is a CI/build failure investigation task. There's an `azdo-build-investigator` skill available that can investigate Azure DevOps pipeline build failures
    and analyze .binlog files. However, this is a GitHub PR URL, not an AZDO URL directly. Let me check if the skill can handle GitHub PR URLs - the skill description says "Use this when users share an AZDO
    build URL, a GitHub PR URL, or ask about a failing pipeline, build errors, or CI failures." So yes, this skill can handle GitHub PR URLs.

    Let me invoke the `azdo-build-investigator` skill.

    ● skill(azdo-build-investigator)

    ◐ Let me follow the skill workflow to investigate the GitHub PR. The URL is #10881.

    First, let me check if `gh` CLI and `az` CLI are available, and then get the failing checks from the PR.

    ● Get failing checks from PR #10881
    $ gh pr checks 10881 --repo dotnet/android --json "name,state,link,bucket" 2>&1
    └ 39 lines...

    ◐ There's one failing check: `Xamarin.Android-PR` with a link to `https://devdiv.visualstudio.com/0bdbc590-a062-4c3f-b0f6-9383f67865ee/_build/results?buildId=13452282`. Let me parse this:
    - Org: `devdiv` (or `devdiv.visualstudio.com`)
    - Project: `0bdbc590-a062-4c3f-b0f6-9383f67865ee`
    - Build ID: `13452282`

    Let me get the build timeline.

    ● Get failed build timeline records
    $ az devops invoke --area build --resource timeline --route-parameters buildId=13452282 --org https://devdiv.visualstudio.com --project 0bdbc590-a062-4c3f-b0f6-9383f67865ee --query "records[?result=='failed']
    | [].{name:name, type:type, issues:issues, errorCount:errorCount}" --output json 2>&1
    └ 6 lines...

    ● Get failed build timeline records with project as route param
    $ az devops invoke --area build --resource timeline --route-parameters project=0bdbc590-a062-4c3f-b0f6-9383f67865ee buildId=13452282 --org https://devdiv.visualstudio.com --query "records[?result=='failed'] |
    [].{name:name, type:type, issues:issues, errorCount:errorCount}" --output json 2>&1
    └ 182 lines...

    ◐ Now I have a clear picture of the failure. The `Xamarin.Android-PR` check is failing in the `Pack .NET Maui` task with 78 RS0016 errors. These are all Roslyn public API analyzer errors — the new symbols
    added by this PR are not registered in the declared public API files.

    The affected files are in `src\AI\src\Essentials.AI\Platform\MaciOS\`:
    1. `NLEmbeddingExtensions.cs` - `NLEmbeddingExtensions` class and `AsIEmbeddingGenerator` method
    2. `NLEmbeddingGenerator.cs` - `NLEmbeddingGenerator` class, constructor, `GenerateAsync`, `Dispose`

    3. `AppleIntelligenceChatClient.cs` - `AppleIntelligenceChatClient` class, constructor, `GetResponseAsync`, `GetStreamingResponseAsync`

    The root cause is that these new public types and members need to be registered in the `PublicAPI.Shipped.txt` or `PublicAPI.Unshipped.txt` file tracked by the `[MAUIAI0001]` analyzer — this is actually a
    MAUI repo issue where the integration build is failing. The fix requires updating the public API declaration file.

    ● The failing check is Xamarin.Android-PR — specifically the "Pack .NET Maui" task, with 78 RS0016 errors.

    -------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------

    Root Cause: Missing Public API Declarations

    The new Apple Intelligence / MAUI AI types added by this PR are not registered in the public API surface file. All errors are RS0016 from the Roslyn PublicApiAnalyzers:

    "Symbol is not part of the declared public API"

    The affected symbols are all in src\AI\src\Essentials.AI\Platform\MaciOS\ (a MAUI repo path, not this repo):

    ┌──────────────────────────────────┬─────────────────────────────────────────────────────────────────────┐
    │ File                             │ New Public Symbols                                                  │
    ├──────────────────────────────────┼─────────────────────────────────────────────────────────────────────┤
    │ AppleIntelligenceChatClient.cs   │ Class, constructor, GetResponseAsync, GetStreamingResponseAsync     │
    ├──────────────────────────────────┼─────────────────────────────────────────────────────────────────────┤
    │ NLEmbeddingGenerator.cs          │ Class, constructor, GenerateAsync, Dispose                          │
    ├──────────────────────────────────┼─────────────────────────────────────────────────────────────────────┤
    │ NLEmbeddingExtensions.cs         │ Class, AsIEmbeddingGenerator extension method                       │
    └──────────────────────────────────┴─────────────────────────────────────────────────────────────────────┘

    Fix

    The PublicAPI.Unshipped.txt file for the [MAUIAI0001] project needs to be updated to include all these new symbols. This is done in the MAUI repo — you need to add entries like:

    [MAUIAI0001]Microsoft.Maui.Essentials.AI.AppleIntelligenceChatClient
    [MAUIAI0001]Microsoft.Maui.Essentials.AI.AppleIntelligenceChatClient.AppleIntelligenceChatClient() -> void
    [MAUIAI0001]Microsoft.Maui.Essentials.AI.AppleIntelligenceChatClient.GetResponseAsync(...) -> ...
    ...

    to the PublicAPI.Unshipped.txt file in that project. The full list of symbols to add can be found in the 78 error messages from the build log.

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

- Clarify prerequisite requirements (az always, gh/binlogtool conditional)
- Fix logs endpoint to save raw text to file instead of requesting JSON

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>