Adopt PromptKit layered configuration sources

docs/roadmap/implementation.md

@@ -1,7 +1,7 @@
 # Implementation Plan: PromptKit v0.12.0 Adoption
 
 **Last updated:** 2026-10-03
-**Status:** In progress; Stages 1–2 completed.
+**Status:** In progress; Stages 1–3 completed.
 **Audience:** Luna coding agent.
 
 ## Scope and Execution
@@ -199,6 +199,13 @@ diff. The obsolete file-reload assertion is intentionally replaced in Stage 6;
 do not restore reload behavior to make that assertion pass. Commit the runtime
 API migration.
 
+**Completion marker:** Stage 3 complete. Runtime construction now uses the
+released PromptKit source API with the selected application mapping; module
+selections match PromptKit v0.12.0 and both `/v3` catalogs at
+`v3.20260930.0`. `go mod tidy`, prompt registry tests, offline profile
+assembly, unsafe-selection, absolute-directory tests, and `git diff --check`
+passed. Captured source accounting remains in Stage 5.
+
 ## Stage 4 — Preserve Startup Failure Classification and Validate Assembly
 
 **Primary files:** `internal/framework/llm/runtime.go`,