ci: replace flaky just.systems curl install with extractions/setup-just action

The just.systems install script intermittently returns HTTP 403, causing
CI jobs to fail before tests even run. The extractions/setup-just GitHub
Action downloads from GitHub releases instead, which is reliable.

Also removes the separate Windows choco install step since the action
handles all platforms natively.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>
Signed-off-by: phernandez <paul@basicmachines.co>

Author: phernandez

.github/workflows/test.yml

@@ -37,17 +37,7 @@ jobs:
         run: |
           pip install uv
 
-      - name: Install just (Linux/macOS)
-        if: runner.os != 'Windows'
-        run: |
-          curl --proto '=https' --tlsv1.2 -sSf https://just.systems/install.sh | bash -s -- --to /usr/local/bin
-
-      - name: Install just (Windows)
-        if: runner.os == 'Windows'
-        run: |
-          # Install just using Chocolatey (pre-installed on GitHub Actions Windows runners)
-          choco install just --yes
-        shell: pwsh
+      - uses: extractions/setup-just@v3
 
       - name: Create virtual env
         run: |
@@ -95,9 +85,7 @@ jobs:
         run: |
           pip install uv
 
-      - name: Install just
-        run: |
-          curl --proto '=https' --tlsv1.2 -sSf https://just.systems/install.sh | bash -s -- --to /usr/local/bin
+      - uses: extractions/setup-just@v3
 
       - name: Create virtual env
         run: |
@@ -131,9 +119,7 @@ jobs:
         run: |
           pip install uv
 
-      - name: Install just
-        run: |
-          curl --proto '=https' --tlsv1.2 -sSf https://just.systems/install.sh | bash -s -- --to /usr/local/bin
+      - uses: extractions/setup-just@v3
 
       - name: Create virtual env
         run: |