refactor: remove hand-rolled dbt parser, use altimate-code CLI instead

Removed the lightweight ref()-based DAG parser (dbt-lightweight.ts).
It was a shortcut that would break on cross-package refs, dynamic refs,
Jinja conditionals, ephemeral models, etc.

Now:
- altimate-code CLI is ALWAYS installed (from GitHub release binaries)
- Impact analysis uses the real CLI tools (impact_analysis, dbt_manifest)
- Static mode = no LLM for SQL review, but dbt analysis uses real tools
- Fallback: CLI-based impact analysis when no manifest available

Also fixed CLI installation:
- Downloads binary directly from GitHub releases (the install script
  at altimate.ai/install redirects to the marketing website)
- Supports linux x64/arm64, darwin x64/arm64
- Caches binary per version

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

Author: anandgupta42

action.yml

@@ -95,31 +95,59 @@ runs:
   steps:
     - name: Get altimate-code version
       id: version
-      if: inputs.mode != 'static'
       shell: bash
       run: |
         VERSION=$(curl -sf -H "Authorization: Bearer ${{ github.token }}" https://api.github.com/repos/AltimateAI/altimate-code/releases/latest | grep -o '"tag_name": *"[^"]*"' | cut -d'"' -f4)
         echo "version=${VERSION:-latest}" >> $GITHUB_OUTPUT
 
     - name: Cache altimate-code
       id: cache
-      if: inputs.mode != 'static'
       uses: actions/cache@v4
       with:
         path: ~/.altimate-code/bin
         key: altimate-code-${{ runner.os }}-${{ runner.arch }}-${{ steps.version.outputs.version }}
 
     - name: Install altimate-code
-      if: inputs.mode != 'static' && steps.cache.outputs.cache-hit != 'true'
+      if: steps.cache.outputs.cache-hit != 'true'
       shell: bash
       run: |
-        # Install altimate-code CLI (required for full/ai modes)
-        npm install -g @anthropic-ai/claude-code@latest 2>/dev/null || \
-        curl -fsSL https://altimate.ai/install | bash || \
-        echo "::warning::altimate-code CLI not available — static mode still works"
+        # Download binary directly from GitHub releases
+        VERSION="${{ steps.version.outputs.version }}"
+        ARCH=$(uname -m)
+        OS=$(uname -s | tr '[:upper:]' '[:lower:]')
+
+        # Map architecture names
+        case "$ARCH" in
+          x86_64) ARCH="x64" ;;
+          aarch64|arm64) ARCH="arm64" ;;
+        esac
+
+        ASSET="altimate-code-${OS}-${ARCH}"
+        if [ "$OS" = "linux" ]; then
+          ASSET="${ASSET}.tar.gz"
+        else
+          ASSET="${ASSET}.zip"
+        fi
+
+        DOWNLOAD_URL="https://github.com/AltimateAI/altimate-code/releases/download/${VERSION}/${ASSET}"
+        echo "Downloading altimate-code ${VERSION} from ${DOWNLOAD_URL}"
+
+        mkdir -p ~/.altimate-code/bin
+        cd /tmp
+        if curl -fsSL -o "altimate-code-archive" "$DOWNLOAD_URL"; then
+          if [ "$OS" = "linux" ]; then
+            tar xzf altimate-code-archive -C ~/.altimate-code/bin/ 2>/dev/null || true
+          else
+            unzip -o altimate-code-archive -d ~/.altimate-code/bin/ 2>/dev/null || true
+          fi
+          chmod +x ~/.altimate-code/bin/altimate-code 2>/dev/null || true
+          rm -f altimate-code-archive
+          echo "altimate-code installed successfully"
+        else
+          echo "::warning::Failed to download altimate-code binary — some features may be limited"
+        fi
 
     - name: Add altimate-code to PATH
-      if: inputs.mode != 'static'
       shell: bash
       run: |
         [ -d "$HOME/.altimate-code/bin" ] && echo "$HOME/.altimate-code/bin" >> $GITHUB_PATH || true