Fix CI: update pixi to v0.63.2 and pin actions to commit SHAs

The lock file was generated with pixi 0.63.2 but CI used v0.46.0,
causing "lock-file not up-to-date" errors.

Author: aktech

.github/workflows/release.yml

@@ -15,9 +15,9 @@ jobs:
       id-token: write
 
     steps:
-      - uses: actions/checkout@v4
+      - uses: actions/checkout@34e114876b0b11c390a56381ad16ebd13914f8d5 # v4
 
-      - uses: actions/setup-python@v5
+      - uses: actions/setup-python@a26af69be951a213d495a4c3e4e4022e16d87065 # v5
         with:
           python-version: "3.12"
 
@@ -28,4 +28,4 @@ jobs:
         run: python -m build
 
       - name: Publish to PyPI
-        uses: pypa/gh-action-pypi-publish@release/v1
+        uses: pypa/gh-action-pypi-publish@ed0c53931b1dc9bd32cbe73a98c7f6766f8a527e # release/v1

.github/workflows/test.yml

@@ -13,11 +13,11 @@ jobs:
     runs-on: ubuntu-latest
 
     steps:
-      - uses: actions/checkout@v4
+      - uses: actions/checkout@34e114876b0b11c390a56381ad16ebd13914f8d5 # v4
 
-      - uses: prefix-dev/setup-pixi@v0.8.1
+      - uses: prefix-dev/setup-pixi@ba3bb36eb2066252b2363392b7739741bb777659 # v0.8.1
         with:
-          pixi-version: v0.46.0
+          pixi-version: v0.63.2
 
       - name: Run tests
         run: pixi run test