ci: drop build_embedchain — embedchain is deprecated

Revert the embedchain matrix restoration. The suite has been broken since
the embedchain Makefile switched from hatch to poetry (install_all calls
`poetry install --all-extras` but the job only installs hatch). Since
embedchain is deprecated, remove the CI block entirely; branch protection
will drop the build_embedchain* contexts in a follow-up admin change.

.github/workflows/ci.yml

@@ -49,7 +49,6 @@ jobs:
     runs-on: ubuntu-latest
     outputs:
       mem0_changed: ${{ steps.filter.outputs.mem0 }}
-      embedchain_changed: ${{ steps.filter.outputs.embedchain }}
     steps:
     - uses: actions/checkout@v4
     - uses: dorny/paths-filter@v2
@@ -61,9 +60,6 @@ jobs:
             - 'tests/**'
             - '.github/workflows/ci.yml'
             - 'pyproject.toml'
-          embedchain:
-            - 'embedchain/**'
-            - '.github/workflows/ci.yml'
 
   build_mem0:
     needs: check_changes
@@ -115,52 +111,3 @@ jobs:
       - name: Run tests and generate coverage report
         if: needs.check_changes.outputs.mem0_changed == 'true'
         run: make test
-
-  build_embedchain:
-    needs: check_changes
-    runs-on: ubuntu-latest
-    strategy:
-      matrix:
-        python-version: ["3.9", "3.10", "3.11", "3.12"]
-    steps:
-      - name: Skip — no embedchain changes
-        if: needs.check_changes.outputs.embedchain_changed != 'true'
-        run: echo "No changes in embedchain/ — skipping"
-      - uses: actions/checkout@v4
-        if: needs.check_changes.outputs.embedchain_changed == 'true'
-      - name: Set up Python ${{ matrix.python-version }}
-        if: needs.check_changes.outputs.embedchain_changed == 'true'
-        uses: actions/setup-python@v4
-        with:
-          python-version: ${{ matrix.python-version }}
-      - name: Install Hatch
-        if: needs.check_changes.outputs.embedchain_changed == 'true'
-        run: pip install hatch
-      - name: Load cached venv
-        if: needs.check_changes.outputs.embedchain_changed == 'true'
-        id: cached-hatch-dependencies
-        uses: actions/cache@v3
-        with:
-          path: .venv
-          key: venv-embedchain-${{ runner.os }}-${{ hashFiles('**/pyproject.toml') }}
-      - name: Install dependencies
-        if: needs.check_changes.outputs.embedchain_changed == 'true' && steps.cached-hatch-dependencies.outputs.cache-hit != 'true'
-        run: cd embedchain && make install_all
-      - name: Run Formatting
-        if: needs.check_changes.outputs.embedchain_changed == 'true'
-        run: |
-          mkdir -p embedchain/.ruff_cache && chmod -R 777 embedchain/.ruff_cache
-          cd embedchain && hatch run format
-      - name: Lint with ruff
-        if: needs.check_changes.outputs.embedchain_changed == 'true'
-        run: cd embedchain && make lint
-      - name: Run tests and generate coverage report
-        if: needs.check_changes.outputs.embedchain_changed == 'true'
-        run: cd embedchain && make coverage
-      - name: Upload coverage reports to Codecov
-        if: needs.check_changes.outputs.embedchain_changed == 'true'
-        uses: codecov/codecov-action@v3
-        with:
-          file: coverage.xml
-        env:
-          CODECOV_TOKEN: ${{ secrets.CODECOV_TOKEN }}