ci(test): reclaim ubuntu runner disk + drop test debug-info (#295)

Ubuntu CI was hitting os error 28 (No space left on device) at link
time — 14 tree-sitter parsers × 30+ test binaries × default debug-info
filled the runner's 14 GB free space (last seen on PR #291 run 26240379100,
tantivy.rlib link failed mid-cascade with callmeta_c_cpp misreported as
the failing test).

Two stacked mitigations:

1. Ubuntu-only `jlumbroso/free-disk-space` step before checkout — drops
   tool-cache + android + dotnet + haskell, reclaiming ~30 GB. macOS &
   windows have 50+ GB free by default; skipped there.
2. Job-level `CARGO_PROFILE_TEST_DEBUG=0` — shrinks target/debug/deps/
   roughly 70%. Assertions stay on; only DWARF data is dropped.

Author: coseto6125

.github/workflows/ci.yml

@@ -158,6 +158,12 @@ jobs:
       matrix:
         os: [ubuntu-latest, macos-latest, windows-latest]
     if: ${{ !(contains(github.event.pull_request.title, '[skip ci]') || contains(github.event.head_commit.message, '[skip ci]')) }}
+    env:
+      # 14 tree-sitter parsers × 30+ test binaries × debug-info defaulted to
+      # `true` produced ~30 GB in target/debug/deps/ and filled the ubuntu
+      # runner's 14 GB free space at link time (tantivy.rlib → os error 28).
+      # Tests run under nextest don't need debug-info; assertions stay on.
+      CARGO_PROFILE_TEST_DEBUG: "0"
 
     steps:
       - name: Short-circuit for docs-only PR
@@ -170,6 +176,19 @@ jobs:
         with:
           egress-policy: audit
 
+      # Reclaim ~30 GB on ubuntu runners before checkout / build. macOS &
+      # windows have 50+ GB free by default; only ubuntu needs this.
+      - name: Free disk space (ubuntu only)
+        if: matrix.os == 'ubuntu-latest'
+        uses: jlumbroso/free-disk-space@54081f138730dfa15788a46383842cd2f914a1be # v1.3.1
+        with:
+          tool-cache: true
+          android: true
+          dotnet: true
+          haskell: true
+          large-packages: false
+          swap-storage: false
+
       - name: Checkout code
         if: needs.detect-changes.outputs.code == 'true'
         uses: actions/checkout@de0fac2e4500dabe0009e67214ff5f5447ce83dd # v6.0.2