fix(ci): include test suites in plan (tests: True), disable fail-fast

cabal v2-test all failed with [Cabal-7043]: 'the solver picked a plan
that does not include the test suites' because the test step, unlike the
build step, replans without --enable-tests. With no project-level
'tests: True' default, the solver drops the bloodhound-tests/doctests
suites and cabal refuses to test (run 28338345700).

- cabal.project: add 'tests: True' so every cabal command (build, test,
  haddock) plans test suites consistently. Matches cabal's diagnostic.
- haskell.yml: set fail-fast: false so one GHC version failing no longer
  cancels the other matrix jobs (which had masked this as cancellations).

Author: blackheaven

.github/workflows/haskell.yml

@@ -35,6 +35,7 @@ jobs:
     needs: generate-matrix
     runs-on: ${{ matrix.os }}
     strategy:
+      fail-fast: false
       matrix: ${{ fromJSON(needs.generate-matrix.outputs.matrix) }}
     steps:
       - uses: actions/checkout@v5

cabal.project

@@ -1,5 +1,7 @@
 packages: *.cabal, examples/*.cabal
 
+tests: True
+
 package bloodhound
 package bloodhound-examples