fix: invalidate ContextFileInterceptor cache on agents.files.set (#29)

* fix: invalidate ContextFileInterceptor cache on agents.files.set

When agents.files.set (or agents.update) wrote context files to
agent_context_files in Postgres, only the agent router cache was
invalidated via agents.InvalidateAgent(). The ContextFileInterceptor
maintains its own separate in-memory cache with a 5-minute TTL which
was never cleared, causing the agent to serve stale file content
(e.g. wizard-written SOUL.md/IDENTITY.md) for up to 5 minutes.

Fix: inject *tools.ContextFileInterceptor into AgentsMethods and call
intc.InvalidateAgent(ag.ID) immediately after each successful DB write
in handleFilesSet and handleUpdate.

Wire path: wireManagedExtras now returns the interceptor it creates;
gateway.go captures it and passes it through registerAllMethods →
NewAgentsMethods. The interceptor is nil in standalone mode so all
nil guards are in place.

* test: add unit tests for ContextFileInterceptor cache invalidation

Covers:
- Cache hit: second read does not call store again
- InvalidateAgent clears agent cache → fresh content served from store
- InvalidateAgent clears user cache for that agent
- InvalidateAgent does not affect other agents' cache entries
- TTL expiry causes re-fetch from store

cmd/gateway_methods.go

@@ -12,12 +12,12 @@ import (
 	"github.com/nextlevelbuilder/goclaw/internal/tools"
 )
 
-func registerAllMethods(server *gateway.Server, agents *agent.Router, sessStore store.SessionStore, cronStore store.CronStore, pairingStore store.PairingStore, cfg *config.Config, cfgPath, workspace, dataDir string, msgBus *bus.MessageBus, execApprovalMgr *tools.ExecApprovalManager, agentStore store.AgentStore, isManaged bool, skillStore store.SkillStore, configSecretsStore store.ConfigSecretsStore, teamStore store.TeamStore) *methods.PairingMethods {
+func registerAllMethods(server *gateway.Server, agents *agent.Router, sessStore store.SessionStore, cronStore store.CronStore, pairingStore store.PairingStore, cfg *config.Config, cfgPath, workspace, dataDir string, msgBus *bus.MessageBus, execApprovalMgr *tools.ExecApprovalManager, agentStore store.AgentStore, isManaged bool, skillStore store.SkillStore, configSecretsStore store.ConfigSecretsStore, teamStore store.TeamStore, contextFileInterceptor *tools.ContextFileInterceptor) *methods.PairingMethods {
 	router := server.Router()
 
 	// Phase 1: Core methods
 	methods.NewChatMethods(agents, sessStore, isManaged, server.RateLimiter()).Register(router)
-	methods.NewAgentsMethods(agents, cfg, cfgPath, workspace, agentStore, isManaged).Register(router)
+	methods.NewAgentsMethods(agents, cfg, cfgPath, workspace, agentStore, isManaged, contextFileInterceptor).Register(router)
 	methods.NewSessionsMethods(sessStore).Register(router)
 	methods.NewConfigMethods(cfg, cfgPath, isManaged, configSecretsStore).Register(router)