ci(darwin): brew reinstall ccache to handle transitive dep drift

Symptom (PR #9752, run 25638825961, job 75256261163):

  dyld[11144]: Library not loaded: /opt/homebrew/opt/fmt/lib/libfmt.12.dylib
    Referenced from: /opt/homebrew/Cellar/ccache/4.13.5/bin/ccache
  Abort trap: 6

Previous fix (commit 3f6e4934) added blake3, hiredis, xxhash, zstd as
explicit installs + cache paths because ccache's runtime dep closure
wasn't in the brew cache. But ccache 4.13 also depends on fmt — which
I missed. This is going to keep happening as upstream ccache adds or
shuffles deps over time.

Durable fix: `brew reinstall ccache` after the install step forces
brew to re-resolve and install ccache's full transitive dep closure
every run, immune to future formula changes. The brew downloads cache
makes the reinstall cheap (~5s on a cache hit).

Also adds fmt to the explicit install/link/Cellar-cache lists for the
fresh-runner path. The reinstall covers the cache-hit path; the
explicit install covers the brand-new-runner path where neither the
downloads cache nor the Cellar cache has been populated yet.

Caught by PR #9752's CI; would also have caught any future
LLAMA_VERSION bump triggering the Darwin matrix.

Assisted-by: Claude:claude-opus-4-7
Signed-off-by: Ettore Di Giacinto <mudler@localai.io>