ci: add crates trusted publishing

.github/workflows/publish-crate.yml

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+name: Publish Rust crate
+
+on:
+  push:
+    branches: [main]
+    paths: ['Cargo.toml']
+
+permissions:
+  contents: read
+
+env:
+  CARGO_TERM_COLOR: always
+
+jobs:
+  check-version:
+    name: Check version change
+    runs-on: ubuntu-latest
+    outputs:
+      changed: ${{ steps.check.outputs.changed }}
+      published: ${{ steps.check.outputs.published }}
+      version: ${{ steps.check.outputs.version }}
+    steps:
+      - uses: actions/checkout@v4
+        with:
+          fetch-depth: 2
+
+      - name: Check if version changed
+        id: check
+        run: |
+          NEW_VERSION=$(python3 -c 'import pathlib, tomllib; print(tomllib.loads(pathlib.Path("Cargo.toml").read_text())["package"]["version"])')
+          OLD_VERSION=$(git show HEAD~1:Cargo.toml | python3 -c 'import sys, tomllib; print(tomllib.loads(sys.stdin.read())["package"]["version"])')
+          echo "old=$OLD_VERSION new=$NEW_VERSION"
+          echo "version=$NEW_VERSION" >> "$GITHUB_OUTPUT"
+
+          if [ "$NEW_VERSION" = "$OLD_VERSION" ]; then
+            echo "changed=false" >> "$GITHUB_OUTPUT"
+            echo "published=false" >> "$GITHUB_OUTPUT"
+            exit 0
+          fi
+
+          echo "changed=true" >> "$GITHUB_OUTPUT"
+
+          HTTP_STATUS=$(curl --silent --show-error --output /tmp/crate-version.json --write-out "%{http_code}" \
+            -H "User-Agent: firecrawl/pdf-inspector publish workflow (https://github.com/firecrawl/pdf-inspector)" \
+            "https://crates.io/api/v1/crates/pdf-inspector/$NEW_VERSION")
+
+          case "$HTTP_STATUS" in
+            200)
+              echo "published=true" >> "$GITHUB_OUTPUT"
+              echo "pdf-inspector v$NEW_VERSION is already published"
+              ;;
+            404)
+              echo "published=false" >> "$GITHUB_OUTPUT"
+              ;;
+            *)
+              cat /tmp/crate-version.json
+              echo "Unexpected crates.io response: $HTTP_STATUS" >&2
+              exit 1
+              ;;
+          esac
+
+  publish:
+    name: Publish to crates.io
+    needs: check-version
+    if: needs.check-version.outputs.changed == 'true' && needs.check-version.outputs.published == 'false'
+    runs-on: ubuntu-latest
+    environment: crates-io
+    permissions:
+      contents: read
+      id-token: write
+    steps:
+      - uses: actions/checkout@v4
+
+      - name: Install Rust
+        uses: dtolnay/rust-toolchain@stable
+
+      - name: Verify package
+        run: cargo publish --dry-run
+
+      - name: Authenticate with crates.io
+        id: auth
+        uses: rust-lang/crates-io-auth-action@v1
+
+      - name: Publish crate
+        run: cargo publish
+        env:
+          CARGO_REGISTRY_TOKEN: ${{ steps.auth.outputs.token }}

docs/publishing.md

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+# Publishing
+
+The Rust crate is published to [crates.io](https://crates.io/crates/pdf-inspector) with trusted publishing from GitHub Actions. The first release was published manually; future releases publish from `.github/workflows/publish-crate.yml` when a `Cargo.toml` version change lands on `main`.
+
+## crates.io Trusted Publisher
+
+Configure the trusted publisher for the `pdf-inspector` crate with:
+
+- Repository: `firecrawl/pdf-inspector`
+- Workflow: `publish-crate.yml`
+- Environment: `crates-io`
+
+The workflow uses `rust-lang/crates-io-auth-action@v1` to exchange GitHub's OIDC token for a short-lived crates.io token, then passes it to `cargo publish`.
+
+## Release Steps
+
+1. Update `version` in `Cargo.toml`.
+2. Merge the version bump to `main`.
+3. The publish workflow compares the new `Cargo.toml` version with `HEAD~1`, runs `cargo publish --dry-run`, then publishes if that version is not already on crates.io.
+
+If `Cargo.toml` changes without a package version bump, the workflow exits without publishing.