Complete the public facade adapter boundary

docs/roadmap/step4.md

@@ -2,9 +2,10 @@
 
 ## Status
 
-Proposed. Migration Steps 1 through 3 are complete; this roadmap defines the
-required target state for Step 4. The separate
-[implementation plan](implementation.md) defines the ordered work.
+Complete as of 2026-07-28. The public-facade adapter boundary is established;
+the [implementation plan](implementation.md) records the completed work, and
+the [main migration roadmap](migration.md) identifies repository creation as
+the next gate.
 
 ## Purpose
 
@@ -19,31 +20,18 @@ owns the long-term project boundary. The
 [main migration roadmap](migration.md) owns the overall sequence. This feature
 roadmap defines the desired Step 4 state, not an implementation sequence.
 
-## Current Gap
+## Achieved Boundary
 
-The public `Engine` facade already supports the ordinary `Prepare` and `Run`
-workflows, directory and alternate framework sources, injected model clients,
-public result values, and broad public error classification. The executable
-adapters do not yet use that boundary consistently:
-
-- the CLI constructs framework repositories, readers, renderer, validator, and
-  OpenAI-compatible client directly, then calls the internal runner;
-- the HTTP handler accepts internal domain request and result values;
-- HTTP error mapping inspects framework-internal sentinels;
-- the HTTP artifact-containment reader implements the internal artifact-reader
-  interface;
-- prepared-run formatting accepts an internal domain value; and
-- adapter tests frequently construct internal runners or use internal domain
-  values.
-
-Those dependencies would prevent Scriptorium from compiling after the
-framework packages move to Promptkit. They also allow the executable to exercise
-a different composition path from downstream Go consumers.
+The CLI, HTTP handler, and prepared-run formatter now consume public engine
+values and errors. `serve` injects Scriptorium's HTTP-owned restricted artifact
+reader through the public extension point, while the root facade continues to
+compose the framework implementation inside this repository. A repository-level
+dependency test protects the direct-import boundary.
 
 ## Target State
 
-At completion, Scriptorium's executable path is an ordinary consumer of the
-same public framework boundary used by other Go applications:
+Scriptorium's executable path is an ordinary consumer of the same public
+framework boundary used by other Go applications:
 
 ```text
 cmd/scriptorium