⚡ perf: add Python dependency caching to all approval workflows

- Enable uv cache in all workflow files (SIG, RFC, Pipeline, Test automation)
- Configure consistent local cache path across all workflows
- Reduces CI build times by sharing cached dependencies between workflow runs
- Improves overall GitHub Actions performance

🤖 Generated with [Claude Code](https://claude.ai/code)

Co-Authored-By: Claude <[email protected]>

Author: kenibrewer

.github/workflows/pipeline_proposals.yml

@@ -18,6 +18,9 @@ jobs:
 
       - name: Setup Python with uv
         uses: astral-sh/setup-uv@v4
+        with:
+          enable-cache: true
+          cache-local-path: .github/workflows/lib/.uv-cache
 
       - name: Install Python dependencies
         working-directory: .github/workflows/lib

.github/workflows/rfc_approval.yml

@@ -18,6 +18,9 @@ jobs:
 
       - name: Setup Python with uv
         uses: astral-sh/setup-uv@v4
+        with:
+          enable-cache: true
+          cache-local-path: .github/workflows/lib/.uv-cache
 
       - name: Install Python dependencies
         working-directory: .github/workflows/lib

.github/workflows/sig_approval.yml

@@ -18,6 +18,9 @@ jobs:
 
       - name: Setup Python with uv
         uses: astral-sh/setup-uv@v4
+        with:
+          enable-cache: true
+          cache-local-path: .github/workflows/lib/.uv-cache
 
       - name: Install Python dependencies
         working-directory: .github/workflows/lib