add doctor command, fix ISBN false positives, wire up CI

ISBN regex now requires an explicit prefix, so it stops matching
years, URLs, job IDs, and dilution ratios.

doctor checks the environment end to end: Python, Tesseract,
PaddleOCR, the PyTorch backend, table/figure detectors, scispaCy,
config, DB, output.

CI runs on 2 OS x 3 Python versions plus a doctor smoke job.
Also added a changelog

.github/workflows/tests.yml

@@ -0,0 +1,65 @@
+name: tests
+
+on:
+  push:
+    branches: [main]
+  pull_request:
+    branches: [main]
+
+concurrency:
+  group: ${{ github.workflow }}-${{ github.ref }}
+  cancel-in-progress: true
+
+jobs:
+  core:
+    name: core (${{ matrix.os }}, py${{ matrix.python-version }})
+    runs-on: ${{ matrix.os }}
+    strategy:
+      fail-fast: false
+      matrix:
+        os: [ubuntu-latest, macos-latest]
+        python-version: ["3.11", "3.12", "3.13"]
+
+    steps:
+      - uses: actions/checkout@v4
+
+      - name: Install uv
+        uses: astral-sh/setup-uv@v3
+        with:
+          enable-cache: true
+          cache-dependency-glob: "uv.lock"
+
+      - name: Set up Python
+        run: uv python install ${{ matrix.python-version }}
+
+      - name: Sync core dependencies
+        run: uv sync --frozen --all-extras
+
+      - name: Install Tesseract (Ubuntu)
+        if: matrix.os == 'ubuntu-latest'
+        run: sudo apt-get update && sudo apt-get install -y tesseract-ocr
+
+      - name: Install Tesseract (macOS)
+        if: matrix.os == 'macos-latest'
+        run: brew install tesseract
+
+      - name: Run ruff
+        run: uv run ruff check src/ tests/
+
+      - name: Check formatting
+        run: uv run ruff format --check src/ tests/
+
+      - name: Run pytest
+        run: uv run pytest tests/ -q --maxfail=1
+
+  doctor-smoke:
+    name: doctor CLI smoke test
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v4
+      - uses: astral-sh/setup-uv@v3
+      - run: uv sync --frozen
+      - name: Install Tesseract
+        run: sudo apt-get update && sudo apt-get install -y tesseract-ocr
+      - name: Run doctor
+        run: uv run ocr-pipeline doctor