Separate Go discovery configuration from diagnostics

docs/roadmap/remediation.md

@@ -2,7 +2,7 @@
 
 Date: 2026-10-06.
 Reviewed source: `55333b0`.
-Status: Two findings require remediation.
+Status: R1 resolved; R2 requires remediation.
 
 ## Scope and assessment
 
@@ -30,7 +30,7 @@ repairs within those decisions.
 
 ## R1 — Medium: Go discovery treats successful diagnostics as invalid configuration
 
-Status: Open.
+Status: Resolved.
 Category: Correctness and an accidental environment prerequisite.
 Introduced by: `0809312`.
 
@@ -67,6 +67,13 @@ the settings. A failing command retains useful stderr and its cause. Existing
 ambient/persistent flag, host-target, cache, and architecture-tuning regressions
 continue to pass. These checks add no warning-free configuration requirement.
 
+**Resolution (2026-10-07):** Discovery captures stdout and stderr separately,
+parses configuration from stdout, and preserves diagnostic output and subprocess
+causes on failure. A subprocess fixture proves successful JSON discovery accepts
+stderr diagnostics and preserves host/cache settings; another verifies failure
+diagnostics and exit-error identity. The success regression failed before the
+fix. Go-environment, candidate-validation, and build regression checks pass.
+
 ## R2 — Medium: Wrapper regression testing repeats the project suite inside itself
 
 Status: Open.