chore(repo): drop .NET implementation in favor of npm-only

The Node port (@kuns/claude-mailbox) is the recommended runtime and
covers all supported features. Maintaining a wire-compatible .NET twin
adds dual-impl tax with no remaining users, so remove src/, tests/,
solution + MSBuild files, NuGet config, and both .NET CI workflows.

Docs updated: README "Path C" build-from-source section dropped,
architecture diagram + Development section simplified, and node/README
no longer subtitles itself as a port of the .NET daemon.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

.gitea/workflows/ci-dotnet.yml

@@ -1,45 +0,0 @@
-name: CI (.NET)
-
-on:
-  push:
-    branches:
-      - main
-    paths:
-      - "src/**"
-      - "tests/**"
-      - "ClaudeMailbox.slnx"
-      - "global.json"
-      - ".gitea/workflows/ci-dotnet.yml"
-  pull_request:
-    branches:
-      - main
-    paths:
-      - "src/**"
-      - "tests/**"
-      - "ClaudeMailbox.slnx"
-      - "global.json"
-      - ".gitea/workflows/ci-dotnet.yml"
-
-jobs:
-  build:
-    runs-on: ubuntu-latest
-    env:
-      DOTNET_ROOT: /home/mika/.dotnet
-    steps:
-      - name: Checkout
-        uses: https://github.com/actions/checkout@v4
-        with:
-          fetch-depth: 0
-
-      - name: Build
-        run: |
-          set -euo pipefail
-          export PATH="$DOTNET_ROOT:$PATH"
-          dotnet build tests/ClaudeMailbox.Tests/ClaudeMailbox.Tests.csproj -c Release
-
-      - name: Test
-        run: |
-          set -euo pipefail
-          export PATH="$DOTNET_ROOT:$PATH"
-          dotnet test tests/ClaudeMailbox.Tests/ClaudeMailbox.Tests.csproj \
-            -c Release --no-build --logger "console;verbosity=normal"

.gitea/workflows/release-dotnet.yml

@@ -1,109 +0,0 @@
-name: Release
-
-on:
-  push:
-    tags:
-      - 'v*'
-
-jobs:
-  release:
-    runs-on: ubuntu-latest
-    env:
-      DOTNET_ROOT: /home/mika/.dotnet
-      GITEA_API: https://git.kuns.dev/api/v1
-      REPO: releases/ClaudeMailbox
-    steps:
-      - name: Checkout tag
-        uses: https://github.com/actions/checkout@v4
-        with:
-          fetch-depth: 0
-
-      - name: Resolve version
-        id: ver
-        run: |
-          set -euo pipefail
-          TAG="${{ github.ref_name }}"
-          VERSION="${TAG#v}"
-          echo "tag=$TAG"         >> "$GITHUB_OUTPUT"
-          echo "version=$VERSION" >> "$GITHUB_OUTPUT"
-          echo "Building version: $VERSION (tag: $TAG)"
-
-      - name: Publish (win-x64, self-contained, single-file)
-        env:
-          VERSION: ${{ steps.ver.outputs.version }}
-        run: |
-          set -euo pipefail
-          export PATH="$DOTNET_ROOT:$PATH"
-          dotnet publish src/ClaudeMailbox/ClaudeMailbox.csproj \
-            -c Release -r win-x64 --self-contained true \
-            /p:MinVerVersionOverride=$VERSION \
-            /p:PublishSingleFile=true \
-            /p:IncludeNativeLibrariesForSelfExtract=true \
-            -o out/app
-
-      - name: Package assets
-        env:
-          VERSION: ${{ steps.ver.outputs.version }}
-        run: |
-          set -euo pipefail
-          mkdir -p assets
-
-          EXE_SRC=$(ls out/app/*.exe | head -n 1)
-          if [ -z "$EXE_SRC" ]; then
-            echo "::error::No .exe produced by publish" >&2
-            exit 1
-          fi
-
-          EXE_NAME="claude-mailbox-${VERSION}-win-x64.exe"
-          cp "$EXE_SRC" "assets/${EXE_NAME}"
-
-          ( cd assets && sha256sum "${EXE_NAME}" > checksums.txt )
-
-          echo "--- assets ---"
-          ls -la assets
-
-      - name: Create Gitea Release
-        id: release
-        env:
-          TAG:   ${{ steps.ver.outputs.tag }}
-          TOKEN: ${{ secrets.GITEA_TOKEN }}
-        run: |
-          set -euo pipefail
-          BODY=$(jq -n \
-            --arg tag  "$TAG" \
-            --arg name "$TAG" \
-            '{tag_name:$tag, name:$name, body:"", draft:false, prerelease:false, target_commitish:"main"}')
-          RESP=$(curl -sS -X POST \
-            -H "Authorization: token ${TOKEN}" \
-            -H "Content-Type: application/json" \
-            -d "$BODY" \
-            "${GITEA_API}/repos/${REPO}/releases")
-          RELEASE_ID=$(echo "$RESP" | jq -r '.id // empty')
-          if [ -z "$RELEASE_ID" ] || [ "$RELEASE_ID" = "null" ]; then
-            echo "::error::Release creation failed" >&2
-            echo "$RESP" >&2
-            exit 1
-          fi
-          echo "release_id=$RELEASE_ID" >> "$GITHUB_OUTPUT"
-          echo "Created release id=$RELEASE_ID for tag=$TAG"
-
-      - name: Upload release assets
-        env:
-          VERSION:    ${{ steps.ver.outputs.version }}
-          RELEASE_ID: ${{ steps.release.outputs.release_id }}
-          TOKEN:      ${{ secrets.GITEA_TOKEN }}
-        run: |
-          set -euo pipefail
-          cd assets
-          for f in \
-            "claude-mailbox-${VERSION}-win-x64.exe" \
-            "checksums.txt"
-          do
-            echo "Uploading: $f"
-            curl -sS --fail-with-body -X POST \
-              -H "Authorization: token ${TOKEN}" \
-              -F "attachment=@${f}" \
-              "${GITEA_API}/repos/${REPO}/releases/${RELEASE_ID}/assets?name=${f}" \
-              > /dev/null
-          done
-          echo "All assets uploaded."

.gitea/workflows/release-node.yml

@@ -85,7 +85,7 @@ jobs:
           TOKEN: ${{ secrets.GITEA_TOKEN }}
         run: |
           set -euo pipefail
-          # Try to find an existing release for this tag (the .NET workflow may have created it).
+          # Try to find an existing release for this tag (idempotent re-runs).
           EXISTING=$(curl -sS \
             -H "Authorization: token ${TOKEN}" \
             "${GITEA_API}/repos/${REPO}/releases/tags/${TAG}" || echo "")