docs(ci): ADR-ci-003 — cross-platform release builds (D1 matrix)

Record the multi-platform build strategy as its own decision: cargo-zigbuild
for the four non-macOS targets, the static/standalone posture per platform,
the Windows synchronization stub, the test->build matrix workflow, and the
macOS deferral with its licensing rationale (the public CI image can't carry
the SDK). Shrinks the ci-001 amendment to a pointer; updates the index.

Runtime-verified by the user: Linux x86_64 + Windows aarch64 run correctly.

docs/ci/adr/20260612-adr-ci-001.md

@@ -24,34 +24,14 @@ it rather than restating it.
 > previously forced website ADRs to be renumbered (see that namespace's
 > history note and ADR-0000 "Numbering discipline").
 
-## Amendment — 2026-06-13: D1 matrix expanded (non-macOS targets)
+## Amendment — 2026-06-13: D1 matrix (non-macOS)
 
-The release now builds the **four non-macOS D1 targets**, all cross-compiled
-from the Linux x86_64 runner with **`cargo-zigbuild`** (Zig's bundled clang +
-libc as one universal cross cc/linker — including the `cc`-crate compile of
-rusqlite's bundled SQLite C — added to the flake devShell, replacing the
-single-target musl cc):
-
-- `x86_64-unknown-linux-musl`, `aarch64-unknown-linux-musl` — static (D2);
-- `x86_64-pc-windows-gnu`, `aarch64-pc-windows-gnullvm` — standalone `.exe`.
-
-`release.yaml` became a **`test` (once, host) → `build` (matrix over the four
-targets)** workflow; each matrix job uploads its artifact + `.sha256` to the
-shared release (idempotent create-or-get).
-
-**Windows link fix:** Rust's std links `-lsynchronization` (WaitOnAddress
-thread-parking), an import lib that rust-overlay's toolchain doesn't ship and
-Zig's mingw lacks. Those symbols are forwarded by `kernel32` (already linked),
-so an **empty stub** `libsynchronization.a` (committed at `ci/winstub/`, wired
-via `.cargo/config.toml` for the Windows targets only) satisfies the linker.
-Verified locally: all four build; the Linux binaries are statically linked; the
-Windows artifacts are valid PE32+ (x86-64 / Aarch64) — not yet runtime
-smoke-tested on Windows.
-
-**macOS stays deferred** (see Deferred): `arboard`→AppKit needs Apple's SDK,
-which a Linux runner can't supply cleanly — and the CI image is *public*, so the
-SDK can't be baked in even if the licensing grey area were accepted. macOS is
-its own step (osxcross + a private SDK, or a real Mac runner).
+§3 (Release) below describes the original **single-target** (x86_64 Linux) job.
+The release is now a **`test` → `build` matrix** over the four non-macOS D1
+targets (Linux + Windows × x86_64/aarch64), cross-built with `cargo-zigbuild`.
+The full decision — tooling, targets, the Windows `synchronization` stub, the
+matrix shape, and the macOS deferral with its licensing rationale — is recorded
+in its own record: **[ADR-ci-003](20260613-adr-ci-003.md)**.
 
 ## Context