refactor: align fork structure with upstream to minimize merge conflicts

Three changes to reduce conflict surface when merging upstream:

1. Move Subagents and SkillsFilter from instanceExt back to
   AgentInstance struct (matches upstream field placement)

2. Remove al *AgentLoop parameter from registerSharedTools to match
   upstream signature. Orchestration registration now happens via
   separate registerAllOrchestrationTools method call in NewAgentLoop

3. Move buildToolsSection from context.go to context_ext.go (fork-only
   code that doesn't exist upstream)

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

pkg/agent/context.go

@@ -157,29 +157,6 @@ Your workspace is at: %s
 		toolsSection, executingRule, toolDiscovery)
 }
 
-func (cb *ContextBuilder) buildToolsSection() string {
-	if cb.tools == nil {
-		return ""
-	}
-
-	summaries := cb.tools.GetSummaries()
-	if len(summaries) == 0 {
-		return ""
-	}
-
-	var sb strings.Builder
-	sb.WriteString("## Available Tools\n\n")
-	sb.WriteString(
-		"**CRITICAL**: You MUST use tools to perform actions. Do NOT pretend to execute commands or schedule tasks.\n\n",
-	)
-	sb.WriteString("You have access to the following tools:\n\n")
-	for _, s := range summaries {
-		sb.WriteString(s)
-		sb.WriteString("\n")
-	}
-	return sb.String()
-}
-
 func (cb *ContextBuilder) getDiscoveryRule() string {
 	if !cb.toolDiscoveryBM25 && !cb.toolDiscoveryRegex {
 		return ""

pkg/agent/context_ext.go

@@ -1,6 +1,10 @@
 package agent
 
-import "github.com/sipeed/picoclaw/pkg/tools"
+import (
+	"strings"
+
+	"github.com/sipeed/picoclaw/pkg/tools"
+)
 
 // contextBuilderExt holds fork-specific fields for ContextBuilder.
 // Embedded in ContextBuilder so existing field access (cb.workDir, cb.tools, etc.) continues to work.
@@ -33,6 +37,30 @@ func (cb *ContextBuilder) SetOrchestrationEnabled(enabled bool) {
 	cb.orchestrationEnabled = enabled
 }
 
+// buildToolsSection generates the "Available Tools" section for the system prompt.
+func (cb *ContextBuilder) buildToolsSection() string {
+	if cb.tools == nil {
+		return ""
+	}
+
+	summaries := cb.tools.GetSummaries()
+	if len(summaries) == 0 {
+		return ""
+	}
+
+	var sb strings.Builder
+	sb.WriteString("## Available Tools\n\n")
+	sb.WriteString(
+		"**CRITICAL**: You MUST use tools to perform actions. Do NOT pretend to execute commands or schedule tasks.\n\n",
+	)
+	sb.WriteString("You have access to the following tools:\n\n")
+	for _, s := range summaries {
+		sb.WriteString(s)
+		sb.WriteString("\n")
+	}
+	return sb.String()
+}
+
 // extIdentityOverrides returns the orchestration-specific overrides for
 // getIdentity: banner prefix, identity string, and plan executing rule.
 // When orchestration is disabled, all return values are empty strings.

pkg/agent/instance.go

@@ -37,6 +37,8 @@ type AgentInstance struct {
 	Sessions                  *session.LegacyAdapter
 	ContextBuilder            *ContextBuilder
 	Tools                     *tools.ToolRegistry
+	Subagents                 *config.SubagentsConfig
+	SkillsFilter              []string
 	Candidates                []providers.FallbackCandidate
 	PlanModel                 string
 	PlanFallbacks             []string

pkg/agent/instance_ext.go

@@ -18,9 +18,6 @@ type instanceExt struct {
 	// Used by runAgentLoop to wait for spawned subagents before worktree cleanup.
 	SubagentMgr *tools.SubagentManager
 
-	Subagents    *config.SubagentsConfig
-	SkillsFilter []string
-
 	// Interview staleness tracking: consecutive turns where MEMORY.md was not updated.
 	interviewStaleCount int
 	interviewMemoryLen  int

pkg/agent/loop.go

@@ -155,8 +155,11 @@ func NewAgentLoop(
 	// Initialize fork-specific fields (stats, sessions, orchestration, gcLoop).
 	al.initLoopExt(cfg, registry, len(enableStats) > 0 && enableStats[0])
 
-	// Register shared tools to all agents (needs al for reporter injection).
-	registerSharedTools(cfg, msgBus, registry, provider, al)
+	// Register shared tools to all agents.
+	registerSharedTools(cfg, msgBus, registry, provider)
+
+	// Register fork-specific orchestration tools (needs al for reporter injection).
+	al.registerAllOrchestrationTools(cfg, registry, provider, msgBus)
 
 	return al
 }
@@ -167,8 +170,6 @@ func registerSharedTools(
 	msgBus *bus.MessageBus,
 	registry *AgentRegistry,
 	provider providers.LLMProvider,
-
-	al *AgentLoop,
 ) {
 	for _, agentID := range registry.ListAgentIDs() {
 		agent, ok := registry.GetAgent(agentID)
@@ -298,9 +299,6 @@ func registerSharedTools(
 			}
 		}
 
-		// Orchestration tools (spawn, subagent, answer, review_plan)
-		registerOrchestrationTools(cfg, agent, agentID, registry, provider, msgBus, al)
-
 		// Update context builder with the complete tools registry
 		agent.ContextBuilder.SetToolsRegistry(agent.Tools)
 	}
@@ -644,7 +642,8 @@ func (al *AgentLoop) ReloadProviderAndConfig(
 	}
 
 	// Ensure shared tools are re-registered on the new registry
-	registerSharedTools(cfg, al.bus, registry, provider, al)
+	registerSharedTools(cfg, al.bus, registry, provider)
+	al.registerAllOrchestrationTools(cfg, registry, provider, al.bus)
 
 	// Atomically swap the config and registry under write lock
 	// This ensures readers see a consistent pair

pkg/agent/loop_ext.go

@@ -107,6 +107,24 @@ func (al *AgentLoop) SetHeartbeatThreadUpdater(fn func(int)) {
 	al.onHeartbeatThreadUpdate = fn
 }
 
+// registerAllOrchestrationTools iterates all agents and registers orchestration
+// tools for those with subagents enabled. Called from NewAgentLoop after
+// registerSharedTools, keeping the upstream function signature clean.
+func (al *AgentLoop) registerAllOrchestrationTools(
+	cfg *config.Config,
+	registry *AgentRegistry,
+	provider providers.LLMProvider,
+	msgBus *bus.MessageBus,
+) {
+	for _, agentID := range registry.ListAgentIDs() {
+		agent, ok := registry.GetAgent(agentID)
+		if !ok {
+			continue
+		}
+		registerOrchestrationTools(cfg, agent, agentID, registry, provider, msgBus, al)
+	}
+}
+
 // registerOrchestrationTools registers spawn, subagent, answer, and review_plan
 // tools for agents with orchestration enabled.
 func registerOrchestrationTools(