refactor(squad): drop dead WorkspaceRefForRun adapter (zero callers)

squad -> workspace import eliminated; physical workspace refs stay
product-side per KTD1. Arch edge removed from allowlist.

.doc/system-design/module-boundaries.yaml

@@ -292,7 +292,6 @@ imports:
     - template
     - textextract
     - workflowdef
-    - workspace
   storage:
     - config
   stream:

internal/squad/workspace_adapter.go

@@ -1,15 +0,0 @@
-package squad
-
-import "chat-agent-system/internal/workspace"
-
-// WorkspaceRefForRun is the only squad→workspace DTO. Physical paths stay inside workspace.
-func WorkspaceRefForRun(runID string, projectID int64, env, token string) workspace.WorkspaceRef {
-	return workspace.WorkspaceRef{
-		ID:            "run-" + runID,
-		SchemaVersion: workspace.SchemaVersion,
-		FencingToken:  token,
-		ProjectScope:  projectID,
-		RunID:         runID,
-		Environment:   env,
-	}
-}