Prune the uv cache at the end of every CI job

The uv cache lives on a persistent volume shared by every job on the
runner (/srv/act-runner-cache/uv), so nothing trimmed it and it grew
without bound. `uv cache prune --ci` drops the entries that are not worth
keeping between runs (pre-built wheels for local sources) while leaving
the downloaded-wheel cache that makes `uv sync` fast.

In bump-version the step carries the same is_merge guard as the rest of
that job, since uv is only set up on a merge push.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

.gitea/workflows/ci.yml

@@ -28,6 +28,9 @@ jobs:
           echo "UV_LINK_MODE=copy" >> "$GITHUB_ENV"
       - run: uv sync --extra cpu --extra dev
       - run: uv run ruff check .
+      # The uv cache is a persistent volume shared by every job on this
+      # runner, so each job trims what it no longer needs before exiting.
+      - run: uv cache prune --ci
 
   ruff-format:
     name: Format (ruff format)
@@ -46,6 +49,7 @@ jobs:
           echo "UV_LINK_MODE=copy" >> "$GITHUB_ENV"
       - run: uv sync --extra cpu --extra dev
       - run: uv run ruff format --check .
+      - run: uv cache prune --ci
 
   type-check:
     name: Type check (ty)
@@ -64,6 +68,7 @@ jobs:
           echo "UV_LINK_MODE=copy" >> "$GITHUB_ENV"
       - run: uv sync --extra cpu --extra dev
       - run: uv run ty check .
+      - run: uv cache prune --ci
 
   test:
     name: Tests
@@ -87,6 +92,7 @@ jobs:
         with:
           name: coverage-report
           path: coverage.xml
+      - run: uv cache prune --ci
 
   bump-version:
     name: Bump version, tag, and update changelog on merge to master
@@ -173,6 +179,10 @@ jobs:
             git tag -a "$TAG" -m "$TAG"
             git push origin "refs/tags/$TAG"
           fi
+      # Same guard as every other step here: on a non-merge push uv was never
+      # set up, so there is nothing to prune.
+      - run: uv cache prune --ci
+        if: steps.merge_check.outputs.is_merge == 'true'
 
   sync-version-on-tag:
     name: Sync project version with tag
@@ -201,3 +211,4 @@ jobs:
           else
             echo "Tag version matches project version ($CURRENT_VERSION)"
           fi
+      - run: uv cache prune --ci