## Summary

Closes the README "Phase 4 — Package distribution" line item so C++
engines (Velox, DuckDB, Iceberg-cpp) can consume `lance-c` through
standard package managers instead of building from a git checkout.

After this PR, every consumer's CMakeLists.txt is a one-liner:

```cmake
find_package(LanceC 0.1 REQUIRED)
target_link_libraries(myapp PRIVATE LanceC::lance_c)
```

…regardless of whether the lib was obtained via `cmake --install`,
`vcpkg install lance-c`, `conan install --requires=lance-c/0.1.0`, or an
unpacked GitHub Release tarball. Transitive platform deps (`-framework
CoreFoundation/Security/SystemConfiguration` on macOS, `pthread/dl/m` on
Linux) are declared once on the imported target — consumers don't
redeclare them.

## What's in the box

- **Top-level `CMakeLists.txt`** wrapping cargo via
[Corrosion](https://github.com/corrosion-rs/corrosion). Opt-in (no
impact on `cargo build`).
- **`LanceC::lance_c{,_static,_shared}` imported targets** +
`LanceCConfig.cmake` package config + `lance-c.pc` pkg-config.
- **Header migration** `include/lance.h` → `include/lance/lance.h` (and
`.hpp`). Convention matches librsvg; breaking for git-checkout vendors
(called out below).
- **`cargo-c` metadata** in `Cargo.toml` for distro packagers who prefer
`cargo cinstall`.
- **Release workflow** (`.github/workflows/release.yml`) building
tarballs on `v*.*.*` tag pushes for 4 triples (Linux+macOS ×
x86_64+aarch64) using native arm64 runners.
- **`consumer-smoke-test`** + **`cbindgen-drift`** jobs added to
`ci.yml`.
- **vcpkg port** at `ports/lance-c/` and **Conan recipe** at
`recipes/lance-c/` — both default to downloading prebuilts (sidesteps
[vcpkg#33824](microsoft/vcpkg#33824)
Rust-in-vcpkg restriction), with `from-source` / `from_source=True`
opt-in.
- **Routine `lance` dep bump 3.0.1 → 4.0.1** as part of pinning a
release version.
- **`examples/cmake-consumer/`** as the smoke-test artifact.

## Breaking change

External consumers vendoring `lance.h` from a git checkout must update:

```diff
-#include "lance.h"
+#include <lance/lance.h>
```

## Test Plan

Acceptance criteria from the spec, status as of this PR:

- [x] **#1** Fresh build + `cmake --install` produces the documented
layout (verified locally on macOS arm64)
- [x] **#2** `examples/cmake-consumer` builds against the install via
`find_package(LanceC)` and runs (verified locally)
- [x] **#7** `cbindgen-drift` job runs in this PR's CI
- [x] **#8** README documents all four install paths and Phase 4 row is
checked off
- [ ] **#3** vcpkg port end-to-end (deferred — needs a published GH
Release with real SHA512s)
- [ ] **#4** Conan recipe end-to-end (deferred — needs published
SHA256s)
- [ ] **#5** Release CI green on `v0.1.0` tag (deferred — happens at
first tag)
- [ ] **#6** Upstream microsoft/vcpkg + conan-io/conan-center-index PRs
(deferred — happens after #5)

## Reference

- Spec:
[`docs/superpowers/specs/2026-04-27-package-distribution-design.md`](docs/superpowers/specs/2026-04-27-package-distribution-design.md)
- Plan:
[`docs/superpowers/plans/2026-04-27-package-distribution.md`](docs/superpowers/plans/2026-04-27-package-distribution.md)
- Velox consumer: facebookincubator/velox#16556 (lands as-is; future PR
can adopt `find_package(LanceC)`)

🤖 Generated with [Claude Code](https://claude.com/claude-code)

---------

Co-authored-by: Claude Opus 4.7 (1M context) <noreply@anthropic.com>