feat(control-plane): af install support for Go agent nodes

PackageMetadata gains an explicit language field with go.mod detection
fallback (additive to config v1; Python manifests unchanged).
entrypoint.build compiles the node at install time via a resolved Go
toolchain (pyinterp-style discovery with actionable missing/too-old
errors); af run launches the built binary with identical port,
healthcheck, secret, and env semantics. Out-of-tree replace directives
are refused with vendoring guidance, with an AGENTFIELD_GO_REPLACE
override for dev installs. Service-layer install/start paths route
through the shared dispatcher so both code paths stay in lockstep.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

Author: AbirAbbas

control-plane/internal/core/services/agent_service.go

@@ -590,11 +590,15 @@ func (as *DefaultAgentService) buildProcessConfig(agentNode packages.InstalledPa
 	}
 
 	// Launch via the manifest entrypoint (e.g. "python -m pr_af.app"). When the
-	// program token is python/python3, substitute the resolved interpreter.
+	// program token is python/python3, substitute the resolved interpreter. A Go
+	// node launches its install-time-built binary; a package-relative binary path
+	// is resolved against the install dir so exec finds it regardless of cwd.
 	startArgs := metadata.StartCommand()
 	command := startArgs[0]
 	args := startArgs[1:]
-	if command == "python" || command == "python3" {
+	if metadata.IsGo() {
+		command = packages.GoBinaryProgram(agentNode.Path, command)
+	} else if command == "python" || command == "python3" {
 		command = pythonPath
 	}
 

control-plane/internal/core/services/package_service.go

@@ -545,9 +545,11 @@ func (ps *DefaultPackageService) copyFile(src, dst string) error {
 	return err
 }
 
-// installDependencies installs package dependencies
+// installDependencies installs package dependencies for the node's language
+// (Go build or Python venv), delegating to the shared, language-aware installer
+// so this service path handles Go nodes identically to the CLI installer.
 func (ps *DefaultPackageService) installDependencies(packagePath string, metadata *packages.PackageMetadata) error {
-	return packages.InstallPythonDependencies(packagePath, metadata.Dependencies.Python, metadata.Dependencies.System)
+	return packages.InstallDependencies(packagePath, metadata)
 }
 
 // hasRequirementsFile checks if requirements.txt exists

control-plane/internal/packages/config_version_fixtures_test.go

@@ -127,6 +127,7 @@ name: pr-af
 version: 0.2.0
 description: Opens draft PRs from a task description
 author: Agent-Field
+language: python
 entrypoint:
   start: python -m pr_af.app
   healthcheck: /health
@@ -167,6 +168,15 @@ user_environment:
 			if md.Name != "pr-af" || md.Version != "0.2.0" {
 				t.Errorf("basics: name=%q version=%q", md.Name, md.Version)
 			}
+			// `language` is an additive optional field (added without a
+			// config_version bump): the current-version fixture asserts the
+			// reader extracts it and that "python" is not treated as a Go node.
+			if md.Language != "python" {
+				t.Errorf("language = %q, want python", md.Language)
+			}
+			if md.IsGo() {
+				t.Errorf("a python node must not be classified as Go")
+			}
 			if got := md.StartCommand(); len(got) == 0 || got[0] != "python" {
 				t.Errorf("StartCommand() = %v", got)
 			}