ci: the portable macOS and Windows jobs run as their own workflow

GitHub serves a job's log only when its whole run has completed, and
the Linux `check` takes over an hour, so a macOS failure's reason was
unreadable for that long while the portable jobs sat in the same run.
Each OS's run now completes on its own; the jobs are unchanged.

Co-Authored-By: Claude Fable 5.1 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01HS8WZziDnyxunC23MUxrLp

.github/workflows/check.yml

@@ -34,43 +34,3 @@ jobs:
       - name: What the build used
         if: always()
         run: df -h / | tail -1
-  # The destination is one installation for macOS, Windows and Linux (D-56,
-  # P11a step 0): the workspace must build and pass its tests on each, not
-  # only here. `just check` (fmt, clippy, rustdoc, proofs' friends) stays
-  # the Linux job's; these run the build and the tests. The job tells
-  # which OS a failure is on; neither is allowed to hide the other.
-  portable:
-    name: portable (${{ matrix.os }})
-    strategy:
-      fail-fast: false
-      matrix:
-        include:
-          - os: macos-latest
-            experimental: false
-          - os: windows-latest
-            experimental: true
-    runs-on: ${{ matrix.os }}
-    continue-on-error: ${{ matrix.experimental }}
-    # Same disk discipline as above: no incremental caches, line tables only.
-    env:
-      CARGO_INCREMENTAL: "0"
-      CARGO_PROFILE_DEV_DEBUG: line-tables-only
-      CARGO_PROFILE_TEST_DEBUG: line-tables-only
-    steps:
-      - uses: actions/checkout@v4
-      - name: Rust (the version mise.toml pins)
-        shell: bash
-        run: rustup toolchain install 1.99 --profile minimal && rustup default 1.99
-      - name: Room for the build
-        shell: bash
-        run: df -h . | tail -1
-      - name: The server-only build (no viewer)
-        run: cargo build -p ledger-cli --no-default-features
-      - name: Everything compiles
-        run: cargo build --workspace --all-targets
-      - name: Tests
-        run: cargo test --workspace
-      - name: What the build used
-        if: always()
-        shell: bash
-        run: df -h . | tail -1