ci: remove Gitea workflow (no runner, solo repo)

The workflow never executed: git.vercanti.com (Gitea 1.24.4) has no
registered act_runner, so it produced 0 runs. Its one check that is not
easily reproduced locally (clean-env import of src/ai_mouse/ to guard the
numpy+onnxruntime-only boundary) can be run by hand before release.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

.github/workflows/ci.yml

@@ -1,37 +0,0 @@
-name: CI
-
-on:
-  push:
-    branches: [main]
-  pull_request:
-    branches: [main]
-
-jobs:
-  library:
-    name: Library tests (no torch)
-    runs-on: ${{ matrix.os }}
-    strategy:
-      fail-fast: false
-      matrix:
-        os: [ubuntu-latest]
-        python: ["3.12", "3.13"]
-    steps:
-      - uses: actions/checkout@v4
-      - uses: astral-sh/setup-uv@v3
-      - run: uv venv --python ${{ matrix.python }}
-      - run: uv pip install -e . pytest
-      - run: uv run pytest tests/unit -v
-
-  dev:
-    name: Full dev suite (with torch)
-    runs-on: ${{ matrix.os }}
-    strategy:
-      fail-fast: false
-      matrix:
-        os: [ubuntu-latest]
-        python: ["3.12", "3.13"]
-    steps:
-      - uses: actions/checkout@v4
-      - uses: astral-sh/setup-uv@v3
-      - run: uv sync --group dev --python ${{ matrix.python }}
-      - run: uv run pytest tests/ -v