fix: address review findings (cache path, docs)

- Composite action: cache to runner.temp instead of /usr/local/bin
  (avoids permission issues on runners)
- Document that temperature=0 means server default (omitted from request)
- Note: strconv import already exists (false positive from GPT-5)

.gitea/actions/review/action.yml

@@ -70,7 +70,7 @@ runs:
       id: cache
       uses: actions/cache@v4
       with:
-        path: /usr/local/bin/review-bot
+        path: ${{ runner.temp }}/review-bot
         key: review-bot-linux-amd64-${{ steps.version.outputs.version }}
 
     - name: Install review-bot
@@ -79,8 +79,8 @@ runs:
       run: |
         GITEA_URL="${{ inputs.gitea-url || github.server_url }}"
         VERSION="${{ steps.version.outputs.version }}"
-        curl -sSfL "${GITEA_URL}/rodin/review-bot/releases/download/${VERSION}/review-bot-linux-amd64" -o /usr/local/bin/review-bot
-        chmod +x /usr/local/bin/review-bot
+        curl -sSfL "${GITEA_URL}/rodin/review-bot/releases/download/${VERSION}/review-bot-linux-amd64" -o ${{ runner.temp }}/review-bot
+        chmod +x ${{ runner.temp }}/review-bot
 
     - name: Run review
       shell: bash
@@ -100,4 +100,4 @@ runs:
         if [ "${{ inputs.dry-run }}" = "true" ]; then
           ARGS="--dry-run"
         fi
-        review-bot $ARGS
+        ${{ runner.temp }}/review-bot $ARGS