Update head.hackage FOD hash and haskell.nix input

The head.hackage upstream content changed (upstream index grew),
making the fixed-output derivation hash in tool-map.nix stale.
With the cached outputs GC'd from hydra builders, all JS backend
IFD evaluations fail with hash mismatch, blocking the entire
Hydra eval (no jobsetevals produced).

Update the head.hackage sha256 from
  sha256-AO/vHIMSIBwjbp5GY561SmnPr5qTTyBt9ruy8D3lKZI=
to
  sha256-nFFut7+8NzUps+4MsmnAo2bLp1EE2Dx4eWqTeZ2aYqI=

Also update haskell.nix from 7e7550c (Dec 2025) to cc939d0
(Feb 23 2026) to pick up latest Hackage/Stackage indexes.

Author: angerman

tool-map.nix

@@ -15,7 +15,7 @@ let
              f76d08be13e9a61a377a85e2fb63f4c5435d40f8feb3e12eb05905edb8cdea89
              26021a13b401500c8eb2761ca95c61f2d625bfef951b939a8124ed12ecf07329
              7541f32a4ccca4f97aea3b22f5e593ba2c0267546016b992dfadcd2fe944e55d
-          --sha256: sha256-AO/vHIMSIBwjbp5GY561SmnPr5qTTyBt9ruy8D3lKZI=
+          --sha256: sha256-nFFut7+8NzUps+4MsmnAo2bLp1EE2Dx4eWqTeZ2aYqI=
 
         if impl(ghc < 9.13)
           active-repositories: hackage.haskell.org