fix(ci): migrate actions/setup-haskell (deprecated) → haskell-actions/setup (#42)

Deprecated action + fake SHA. Replaced with the canonical
haskell-actions/setup v2.11.0 used estate-wide. Same
ghc-version/cabal-version interface; behavioural drop-in. Provenance:
project_estate_fake_action_sha_punch_list_2026_05_30.

Author: hyperpolymath

.github/workflows/haskell.yml

@@ -18,7 +18,7 @@ jobs:
 
     steps:
     - uses: actions/checkout@de0fac2e4500dabe0009e67214ff5f5447ce83dd # v6.0.2
-    - uses: actions/setup-haskell@28c8ff1d6cbeaed15ce310b1952dc19352a0a07d # v1.1.5
+    - uses: haskell-actions/setup@cd0d9bdd65b20557f41bea4dbe43d0b5fbbfe553 # v2.11.0
       with:
         ghc-version: '8.10.3'
         cabal-version: '3.2'