Build selected targets with version injection

docs/roadmap/implementation.md

@@ -1,7 +1,6 @@
 # ReleaseKit staged implementation plan
 
-Status: Proposed. All stages are pending; this document introduces no implemented
-features or published contracts.
+Status: In progress. Stages 1–10 are complete; later stages remain pending.
 
 Date: 2026-10-05
 
@@ -683,7 +682,7 @@ ReleaseKit release was published.
 
 ## Stage 10: Build selected targets with shared version injection
 
-Status: Pending. Depends on Stage 9.
+Status: Complete. Depends on Stage 9.
 
 1. Implement public build values and internal build execution using the fixed
    flags, version symbol, filename convention, and prepared Go environment.
@@ -702,6 +701,17 @@ does not select the smoke host. Empty targets perform no build or smoke test;
 missing main packages, build failures, incorrect version output, unsafe binary
 names, and cancellation fail with useful partial results.
 
+Evidence: `releasekit.Build` and `internal/build` compile Linux amd64, Linux
+arm64, and macOS arm64 artifacts using the shared linker symbol and prepared
+local Go environment. The consumer fixture imports `buildinfo` and reports the
+injected version through its `version` invocation. Results retain the observed
+source commit, compiler identity, normalized targets, absolute paths, filenames,
+and SHA-256 digests. Tests cover host selection despite ambient cross-target
+variables, empty target sets, existing output preservation, partial target
+failure, missing packages, incorrect version output, unsafe names, and
+cancellation with completed artifacts retained. No byte-reproducibility or
+cross-platform execution guarantee is added.
+
 ## Stage 11: Integrate candidate builds and artifact command
 
 Status: Pending. Depends on Stage 10.