ci: Add DATADEPS_ALWAYS_ACCEPT for remote dataset downloads

Fixes #61

DataDeps.jl requires the DATADEPS_ALWAYS_ACCEPT environment variable
to be set in CI environments to automatically accept data dependency
downloads without user interaction. Without this, downloads of remote
datasets from Figshare fail with HTTP 403 errors on macOS runners.

This is a standard requirement for using DataDeps.jl in CI, as
documented in the DataDeps.jl documentation.

Author: claude

.github/workflows/ci.yml

@@ -11,6 +11,8 @@ jobs:
   test:
     name: Julia ${{ matrix.julia-version }} - ${{ matrix.os }}
     runs-on: ${{ matrix.os }}
+    env:
+      DATADEPS_ALWAYS_ACCEPT: true
     strategy:
       fail-fast: false
       matrix:
@@ -35,6 +37,13 @@ jobs:
           key: ${{ runner.os }}-${{ env.cache-name }}-${{ hashFiles('docs/CondaPkg.toml') }}
           restore-keys: |
             ${{ runner.os }}-${{ env.cache-name }}-
+      - name: Cache DataDeps
+        uses: actions/cache@v4
+        with:
+          path: ~/.julia/datadeps
+          key: ${{ runner.os }}-datadeps-${{ hashFiles('**/Project.toml') }}
+          restore-keys: |
+            ${{ runner.os }}-datadeps-
       - uses: julia-actions/julia-buildpkg@latest
       - uses: julia-actions/julia-runtest@latest
       - uses: julia-actions/julia-processcoverage@v1