chore: bootstrap ShellSyntaxTree from Akka template (#3)

Strip inherited Akka.NET build-system-template artifacts and stand up
the agent operating system for the ShellSyntaxTree library:

- Remove `.azure/`, `src/Akka.Console/`, `akkalogo.png`, `build.ps1`,
  legacy release-notes PowerShell, DocFX local tool, Akka.Hosting and
  Microsoft.Extensions.Hosting package references, Akka.Event global
  Using.
- Rewrite `Directory.Build.props` and `Directory.Packages.props` for
  Aaron Stannard attribution, ShellSyntaxTree NuGet metadata, xUnit
  test stack, and SourceLink. `VersionPrefix=0.1.0`,
  `VersionSuffix=alpha`.
- Rename `SampleSln.slnx` to `ShellSyntaxTree.slnx`; rewrite README
  to describe the library rather than the build template.
- Update CI: `pr_validation.yml` runs build/test/pack and verifies
  copyright headers; `publish_nuget.yml` triggers on `v*.*.*` tags
  and computes the package version from the tag.
- Add agent OS files: `PROJECT_CONTEXT.md`, `TOOLING.md`, `AGENTS.md`,
  `IMPLEMENTATION_PLAN.md`. `CLAUDE.md` is a symlink to `AGENTS.md`.
- Add `SPEC.md` (the locked v0.1 contract).
- Add `scripts/Add-FileHeaders.ps1` (Aaron Stannard copyright header
  enforcement, modeled on the Netclaw equivalent) covering `src/` and
  `tests/`. CI runs `-Verify`.
- Generate and commit a NuGet package icon (`assets/icon.png`,
  512x512) wired into `Directory.Build.props` via `PackageIcon`.

Author: Aaronontheweb

.azure/azure-pipeline.template.yaml

@@ -8,13 +8,6 @@
         "incrementalist"
       ],
       "rollForward": false
-    },
-    "docfx": {
-      "version": "2.78.3",
-      "commands": [
-        "docfx"
-      ],
-      "rollForward": false
     }
   }
-}
+}

.azure/pr-validation.yaml

@@ -36,19 +36,19 @@ jobs:
       - name: "Restore .NET tools"
         run: dotnet tool restore
 
-      - name: "Update release notes"
+      - name: "Verify copyright headers"
         shell: pwsh
-        run: |
-          ./build.ps1
+        run: ./scripts/Add-FileHeaders.ps1 -Verify
 
-      - name: "dotnet build"
-        run: dotnet build -c Release
+      - name: "dotnet restore"
+        run: dotnet restore
 
-      # .NET Framework tests can't run reliably on Linux, so we only do .NET 8
+      - name: "dotnet build"
+        run: dotnet build -c Release --no-restore
 
       - name: "dotnet test"
         shell: bash
-        run: dotnet test -c Release 
+        run: dotnet test -c Release --no-build
 
       - name: "dotnet pack"
-        run: dotnet pack -c Release -o ./bin/nuget
+        run: dotnet pack -c Release --no-build -o ./bin/nuget

.azure/windows-release.yaml

@@ -3,72 +3,69 @@ name: Publish NuGet
 on:
   push:
     tags:
-      - '*'
+      - 'v*.*.*'
+      - 'v*.*.*-*'
 
 permissions:
-   contents: write
+  contents: write
 
 jobs:
   publish-nuget:
-
     name: publish-nuget
-    runs-on: ${{ matrix.os }}
-    strategy:
-      matrix:
-        os: [ubuntu-latest]
+    runs-on: ubuntu-latest
 
     steps:
-    - name: "Checkout"
-      uses: actions/checkout@v6.0.2
-      with:
-        lfs: true
-        fetch-depth: 0
-        
-    - name: "Install .NET SDK"
-      uses: actions/setup-dotnet@v5.1.0
-      with:
-        global-json-file: "./global.json"
+      - name: "Checkout"
+        uses: actions/checkout@v6.0.2
+        with:
+          lfs: true
+          fetch-depth: 0
 
-    - name: "Restore .NET tools"
-      run: dotnet tool restore
+      - name: "Install .NET SDK"
+        uses: actions/setup-dotnet@v5.1.0
+        with:
+          global-json-file: "./global.json"
 
-    - name: "Update release notes"
-      shell: pwsh
-      run: |
-        ./build.ps1
+      - name: "Restore .NET tools"
+        run: dotnet tool restore
 
-    - name: Create Packages
-      run:  dotnet pack /p:PackageVersion=${{ github.ref_name }} -c Release -o ./output
+      - name: "Compute package version from tag"
+        shell: bash
+        run: |
+          # tag form is vX.Y.Z or vX.Y.Z-suffix
+          TAG="${GITHUB_REF_NAME}"
+          VERSION="${TAG#v}"
+          echo "PACKAGE_VERSION=${VERSION}" >> "$GITHUB_ENV"
+          echo "Publishing package version: ${VERSION}"
 
-    - name: Push Packages
-      run: dotnet nuget push "output/*.nupkg" -k ${{ secrets.NUGET_KEY }} -s https://api.nuget.org/v3/index.json
+      - name: "dotnet pack"
+        run: dotnet pack /p:PackageVersion=${{ env.PACKAGE_VERSION }} -c Release -o ./output
 
-    - name: "Extract latest release notes"
-      shell: pwsh
-      run: |
-        $content = Get-Content RELEASE_NOTES.md -Raw
-        # Match from the first #### heading to just before the second one
-        if ($content -match '(?s)(####.+?)(?=\n####|\z)') {
-          $Matches[1].Trim() | Set-Content RELEASE_NOTES_LATEST.md
-        } else {
-          $content | Set-Content RELEASE_NOTES_LATEST.md
-        }
+      - name: "dotnet nuget push"
+        run: dotnet nuget push "output/*.nupkg" -k ${{ secrets.NUGET_KEY }} -s https://api.nuget.org/v3/index.json --skip-duplicate
 
-    - name: release
-      uses: actions/create-release@v1
-      id: create_release
-      with:
-        draft: false
-        prerelease: false
-        release_name: 'Akka.Hosting ${{ github.ref_name }}'
-        tag_name: ${{ github.ref }}
-        body_path: RELEASE_NOTES_LATEST.md
-      env:
-        GITHUB_TOKEN: ${{ github.token }}
+      - name: "Extract latest release notes"
+        shell: pwsh
+        run: |
+          if (-not (Test-Path RELEASE_NOTES.md)) {
+            "No release notes available." | Set-Content RELEASE_NOTES_LATEST.md
+            exit 0
+          }
+          $content = Get-Content RELEASE_NOTES.md -Raw
+          if ($content -match '(?s)(####.+?)(?=\n####|\z)') {
+            $Matches[1].Trim() | Set-Content RELEASE_NOTES_LATEST.md
+          } else {
+            $content | Set-Content RELEASE_NOTES_LATEST.md
+          }
 
-    - name: Upload Release Asset
-      uses: AButler/upload-release-assets@v3.0
-      with:
-          repo-token: ${{ github.token }}
-          release-tag: ${{ github.ref_name }}
-          files: 'output/*.nupkg'
+      - name: "Create GitHub release"
+        uses: softprops/action-gh-release@v2
+        with:
+          name: "ShellSyntaxTree ${{ github.ref_name }}"
+          tag_name: ${{ github.ref_name }}
+          body_path: RELEASE_NOTES_LATEST.md
+          files: output/*.nupkg
+          draft: false
+          prerelease: ${{ contains(github.ref_name, '-') }}
+        env:
+          GITHUB_TOKEN: ${{ github.token }}