app-build.yml does not trigger on StrandTests/**, so a test-only PR verifies nothing #1954

app-build.yml is what compiles the app targets and runs the app-target tests:

      - name: Test ${{ matrix.scheme }}
        if: matrix.scheme == 'Strand'

Its trigger lists the sources but not the tests:

    paths:
      - 'Strand/**'
      - 'StrandiOS/**'
      - 'StrandiOSShared/**'
      - 'StrandiOSWidgets/**'
      - 'Packages/**'
      - 'project.yml'
      - '.github/workflows/app-build.yml'

StrandTests/** is absent. A PR that touches only app-target tests therefore
builds nothing and runs nothing, so a test file that does not compile, or one
that fails, merges unverified and then fails on the next unrelated PR that
happens to touch Strand/**.

Why it matters more than it looks

StrandTests is where the app-target logic lives that the Swift packages cannot
reach: backfill continuation, scheduled-report and strain-target policy, and the
source-guard tests that pin call-site invariants no unit test can drive. Adding
one of those is a common shape of change, and it is precisely the shape this
filter does not cover.

The failure is also mis-attributed when it lands: the PR that goes red is the one
that touched Strand/**, not the one that introduced the broken test.

Fix

Add StrandTests/** to the same paths list. One line, no new job, no extra
macOS minutes except on PRs that genuinely change those tests.

Found while confirming that a new guard test in #1951 would actually run in CI.
It does, but only because that PR also edits BLEManager.swift.