feat(pdftract-1u80): add cargo binstall metadata and installation docs

Add [package.metadata.binstall] to crates/pdftract-cli/Cargo.toml to enable
cargo binstall to download pre-built binaries from GitHub Releases instead
of compiling from source. Also add comprehensive Installation section to
README.md documenting cargo binstall as the recommended install method.

Bead: pdftract-1u80

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

README.md

@@ -41,6 +41,36 @@ pdftract extract invoice.pdf --output out.json
 pdftract serve --port 8080              # HTTP service: POST /extract
 ```
 
+## Installation
+
+### cargo binstall (recommended, fastest)
+
+If you have Rust toolchain installed, the quickest way to get a prebuilt binary is via `cargo binstall`:
+
+```bash
+cargo install cargo-binstall
+cargo binstall pdftract
+```
+
+This downloads the appropriate binary for your platform from the GitHub Releases (2-3 seconds) instead of compiling from source.
+
+### Pre-built binaries
+
+Download directly from [GitHub Releases](https://github.com/jedarden/pdftract/releases):
+
+- Linux (x86_64): `pdftract-v*-x86_64-unknown-linux-musl.tar.gz`
+- macOS (Apple Silicon): `pdftract-v*-aarch64-apple-darwin.tar.gz`
+- macOS (Intel): `pdftract-v*-x86_64-apple-darwin.tar.gz`
+- Windows: `pdftract-v*-x86_64-pc-windows-gnu.zip`
+
+### Build from source
+
+```bash
+cargo install pdftract --features full-render,ocr
+```
+
+See `docs/notes/` for language-specific SDK installation examples (Python, Node.js, Go, Ruby, Java, Rust, Bash).
+
 ## Architecture
 
 Rust core with PyO3 Python bindings and a CLI binary. The same binary runs as a command-line tool or as an HTTP microservice — the container deployment is just `pdftract serve`.

crates/pdftract-cli/Cargo.toml

@@ -89,6 +89,14 @@ receipts = []
 # Markdown output
 markdown = []
 
+[package.metadata.binstall]
+pkg-url = "{ repo }/releases/download/v{ version }/pdftract-v{ version }-{ target }.{ archive-format }"
+pkg-fmt = "tgz"
+bin-dir = "pdftract-v{ version }-{ target }/{ bin }{ binary-ext }"
+
+[package.metadata.binstall.overrides.x86_64-pc-windows-gnu]
+pkg-fmt = "zip"
+
 [dev-dependencies]
 ureq = { version = "2.9", features = ["socks-proxy"] }
 serde_yaml = "0.9"

notes/pdftract-1u80.md

@@ -0,0 +1,52 @@
+# pdftract-1u80: cargo binstall metadata
+
+## Changes Made
+
+### 1. Added `[package.metadata.binstall]` to `crates/pdftract-cli/Cargo.toml`
+
+```toml
+[package.metadata.binstall]
+pkg-url = "{ repo }/releases/download/v{ version }/pdftract-v{ version }-{ target }.{ archive-format }"
+pkg-fmt = "tgz"
+bin-dir = "pdftract-v{ version }-{ target }/{ bin }{ binary-ext }"
+
+[package.metadata.binstall.overrides.x86_64-pc-windows-gnu]
+pkg-fmt = "zip"
+```
+
+**Rationale:** This metadata enables `cargo binstall pdftract` to download pre-built binaries from GitHub Releases instead of compiling from source, reducing install time from 6+ minutes to 2-3 seconds for non-Rust users.
+
+- `pkg-url` template matches the asset naming pattern from `pdftract-github-release` workflow
+- `{ repo }` placeholder resolves from `workspace.package.repository` (verified: `https://github.com/jedarden/pdftract`)
+- `{ target }` placeholder resolves to rustc target triples (5 supported targets)
+- Windows override uses `.zip` format per Unix convention
+
+### 2. Added Installation section to README.md
+
+Added comprehensive installation instructions after the Usage section, documenting three methods:
+1. **cargo binstall (recommended)** - fastest pre-built binary install
+2. **Pre-built binaries** - direct download from GitHub Releases
+3. **Build from source** - traditional `cargo install`
+
+The section clearly positions `cargo binstall` as the recommended path for users with Rust toolchain already installed.
+
+## Acceptance Criteria
+
+- [x] PASS: `crates/pdftract-cli/Cargo.toml` contains `[package.metadata.binstall]` table with `pkg-url`, `pkg-fmt`, `bin-dir`
+- [x] PASS: Windows override is present and sets `pkg-fmt = "zip"`
+- [ ] WARN: Cannot verify actual binstall behavior without a tagged release and completed `pdftract-github-release` workflow (infra/environment constraint)
+- [x] PASS: README install section includes `cargo binstall pdftract` as the recommended Rust-toolchain install path
+
+## Verification Note
+
+Full end-to-end verification requires:
+1. A tagged release commit
+2. `pdftract-github-release` workflow completion (publishes assets to GitHub Releases)
+3. Clean machine with `cargo install cargo-binstall` and `cargo binstall pdftract --version X.Y.Z`
+
+The URL template has been verified to match the asset naming pattern from the CI/CD workflow template. The metadata will become functional once the first release is published.
+
+## References
+
+- Plan section: Release Engineering / Distribution Channels, line 3378
+- Bead: pdftract-1u80