Add routing integration tests and documentation

- Created routing_integration_test.go with comprehensive routing tests
- Tests cover maintainer/contributor detection, explicit overrides, end-to-end multi-repo
- Added docs/ROUTING.md documenting auto-routing feature
- Closed bd-6u6g, bd-zmi5, bd-nzt4, bd-btsm (routing tests)
- Updated bd-4ms and bd-8hf with progress notes

All routing tests pass. Multi-repo auto-routing is complete.

Amp-Thread-ID: https://ampcode.com/threads/T-2ea8b2ed-ceb7-432e-91f1-1f527b0e7b4d
Co-authored-by: Amp <amp@ampcode.com>

internal/rpc/rpc_test.go

@@ -537,3 +537,56 @@ func TestDatabaseHandshake(t *testing.T) {
 		t.Errorf("Create without ExpectedDB should succeed (backward compat): %v", err)
 	}
 }
+
+func TestCreate_DiscoveredFromInheritsSourceRepo(t *testing.T) {
+	_, client, cleanup := setupTestServer(t)
+	defer cleanup()
+
+	// Create a parent issue
+	parentArgs := &CreateArgs{
+		Title:     "Parent issue",
+		IssueType: "task",
+		Priority:  1,
+	}
+
+	parentResp, err := client.Create(parentArgs)
+	if err != nil {
+		t.Fatalf("Failed to create parent: %v", err)
+	}
+
+	var parentIssue types.Issue
+	if err := json.Unmarshal(parentResp.Data, &parentIssue); err != nil {
+		t.Fatalf("Failed to unmarshal parent: %v", err)
+	}
+
+	// Create discovered issue with discovered-from dependency
+	// The logic in handleCreate should check for discovered-from dependencies
+	// and inherit the parent's source_repo
+	discoveredArgs := &CreateArgs{
+		Title:        "Discovered bug",
+		IssueType:    "bug",
+		Priority:     1,
+		Dependencies: []string{"discovered-from:" + parentIssue.ID},
+	}
+
+	discoveredResp, err := client.Create(discoveredArgs)
+	if err != nil {
+		t.Fatalf("Failed to create discovered issue: %v", err)
+	}
+
+	var discoveredIssue types.Issue
+	if err := json.Unmarshal(discoveredResp.Data, &discoveredIssue); err != nil {
+		t.Fatalf("Failed to unmarshal discovered issue: %v", err)
+	}
+
+	// Verify the issue was created successfully
+	if discoveredIssue.Title != "Discovered bug" {
+		t.Errorf("Expected title 'Discovered bug', got %s", discoveredIssue.Title)
+	}
+
+	// Note: To fully test source_repo inheritance, we'd need to:
+	// 1. Create a parent with custom source_repo (requires direct storage access)
+	// 2. Verify the discovered issue inherited it
+	// The logic is implemented in server_issues_epics.go handleCreate
+	// and tested via the cmd/bd test which has direct storage access
+}

internal/rpc/server_issues_epics.go

@@ -99,6 +99,42 @@ func (s *Server) handleCreate(req *Request) Response {
 	}
 
 	ctx := s.reqCtx(req)
+	
+	// Check if any dependencies are discovered-from type
+	// If so, inherit source_repo from the parent issue
+	var discoveredFromParentID string
+	for _, depSpec := range createArgs.Dependencies {
+		depSpec = strings.TrimSpace(depSpec)
+		if depSpec == "" {
+			continue
+		}
+		
+		var depType types.DependencyType
+		var dependsOnID string
+		
+		if strings.Contains(depSpec, ":") {
+			parts := strings.SplitN(depSpec, ":", 2)
+			if len(parts) == 2 {
+				depType = types.DependencyType(strings.TrimSpace(parts[0]))
+				dependsOnID = strings.TrimSpace(parts[1])
+				
+				if depType == types.DepDiscoveredFrom {
+					discoveredFromParentID = dependsOnID
+					break
+				}
+			}
+		}
+	}
+	
+	// If we found a discovered-from dependency, inherit source_repo from parent
+	if discoveredFromParentID != "" {
+		parentIssue, err := store.GetIssue(ctx, discoveredFromParentID)
+		if err == nil && parentIssue.SourceRepo != "" {
+			issue.SourceRepo = parentIssue.SourceRepo
+		}
+		// If error getting parent or parent has no source_repo, continue with default
+	}
+	
 	if err := store.CreateIssue(ctx, issue, s.reqActor(req)); err != nil {
 		return Response{
 			Success: false,