agent: inject baseLayers (system prompt, operational model, env) into /agent reload path

The operational model was only rendered for new sessions, not for
restored sessions or /agent reloads. Store baseLayers on the agent
struct and pass them through on rebuild.

Also fix pre-existing test failures caused by DiscoverTools reading
from the live OLLIE_TOOLS_PATH during tests.

pkg/agent/commands.go

@@ -177,7 +177,7 @@ func (s *agent) handleCommand(ctx context.Context, input string) bool {
 			d := s.newDispatcher()
 			env := []string{"OLLIE_SESSION_ID=" + s.sessionID, "OLLIE_UNAME=" + s.uname}
 			env = append(env, s.promptEnvExtra...)
-			rt := BuildRuntime(cfg, d, s.cwd, env)
+			rt := BuildRuntime(cfg, d, s.cwd, env, s.baseLayers...)
 			if rt.CfgBackend != "" {
 				newBe, err := s.newBackend(rt.CfgBackend)
 				if err != nil {

pkg/agent/core.go

@@ -283,13 +283,10 @@ type AgentCoreConfig struct {
 	PromptEnvExtra []string
 	// Remote is the SSH target for remote execution (empty = local).
 	Remote string
-	// OperationalModel is server-injected text describing the 9P/D-Bus
-	// interface available to the agent. Not user-configurable.
-	OperationalModel string
-	// SystemPrompt is the base system prompt text (embedded default or
-	// override from agent config / session creation). If empty, BuildRuntime
-	// uses only the agent config's prompt commands.
-	SystemPrompt string
+	// BaseLayers are the system prompt, operational model, and environment
+	// block prepended to the agent preamble. Stored so /agent reloads
+	// preserve the server-injected context.
+	BaseLayers []string
 }
 
 // agent is the Core implementation. It owns all agent and session state
@@ -312,6 +309,7 @@ type agent struct {
 	cwd             string
 	remote          string   // SSH target for remote execution
 	promptEnvExtra  []string // PRIME_* vars for prompt resolution
+	baseLayers      []string // system prompt, operational model, env block — for /agent reloads
 	startupMessages  []string
 	currentAction   atomic.Pointer[actionHandle]
 	toolCallCount   atomic.Int64
@@ -479,6 +477,7 @@ func NewAgentCore(cfg AgentCoreConfig) Core {
 		cwd:             paths.ExpandHome(cfg.CWD),
 		remote:          cfg.Remote,
 		promptEnvExtra:  cfg.PromptEnvExtra,
+		baseLayers:      cfg.BaseLayers,
 		startupMessages: rt.Messages,
 		newDispatcher:   cfg.NewDispatcher,
 		newBackend:      cfg.NewBackend,

pkg/agent/core_test.go

@@ -2321,6 +2321,7 @@ func setupCfgDir(t *testing.T) string {
 	t.Helper()
 	dir := t.TempDir()
 	t.Setenv("OLLIE_CFG_PATH", dir)
+	t.Setenv("OLLIE_TOOLS_PATH", filepath.Join(dir, "tools"))
 	return dir
 }