Add profile loading and process execution

docs/roadmap/implementation.md

@@ -510,7 +510,7 @@ checker command and internal package inventory to the canonical developer docs.
 
 ## Stage 4: Implement profile loading and command adaptation
 
-Status: Pending. Depends on Stage 3.
+Status: Complete. Depends on Stage 3.
 
 1. Implement JSON product, remote, and command settings under an internal CLI
    adapter. Add strict field decoding, directory resolution, required-value
@@ -527,6 +527,15 @@ selected environment values reach the child without changing process globals;
 missing executables, invalid configuration, and cancellation report useful
 errors. Tests use controlled local child commands and temporary directories.
 
+Completion evidence: added strict profile decoding, repository-relative and
+absolute profile resolution, required product and command diagnostics, and
+direct check argument adaptation. Added a cancellable `os/exec` runner with
+working directory, inherited environment plus child-only overlays, stdout,
+stderr, and preserved exit errors. Tests cover spaced paths and arguments,
+environment isolation, missing executables, exit failures, cancellation, and
+invalid profiles. Added a profile example and canonical CLI, configuration, and
+internal package documentation.
+
 ## Stage 5: Capture and validate one local candidate
 
 Status: Pending. Depends on Stage 4.