feat: lifecycle context — Core.Context() for cooperative shutdown

- Core holds context.Context + CancelFunc
- New() creates background context
- ServiceStartup creates fresh context from caller's ctx (restart safe)
- ServiceShutdown cancels context before draining tasks
- c.Context() accessor lets task handlers check Done() for graceful exit

Co-Authored-By: Virgil <virgil@lethean.io>

pkg/core/contract.go

@@ -86,6 +86,7 @@ func New(opts ...Options) *Core {
 		services: &serviceRegistry{services: make(map[string]*Service)},
 		commands: &commandRegistry{commands: make(map[string]*Command)},
 	}
+	c.ctx, c.cancel = context.WithCancel(context.Background())
 
 	if len(opts) > 0 {
 		cp := make(Options, len(opts[0]))

pkg/core/core.go

@@ -6,6 +6,7 @@
 package core
 
 import (
+	"context"
 	"sync"
 	"sync/atomic"
 )
@@ -29,6 +30,8 @@ type Core struct {
 	ipc     *Ipc     // c.IPC()            — Message bus for IPC
 	i18n    *I18n    // c.I18n()           — Internationalisation and locale collection
 
+	ctx           context.Context
+	cancel        context.CancelFunc
 	taskIDCounter atomic.Uint64
 	wg            sync.WaitGroup
 	shutdown      atomic.Bool
@@ -48,6 +51,7 @@ func (c *Core) Log() *ErrorLog      { return c.log }
 func (c *Core) Cli() *Cli         { return c.cli }
 func (c *Core) IPC() *Ipc         { return c.ipc }
 func (c *Core) I18n() *I18n       { return c.i18n }
+func (c *Core) Context() context.Context { return c.ctx }
 func (c *Core) Core() *Core       { return c }
 
 // --- IPC (uppercase aliases) ---

pkg/core/runtime.go

@@ -34,6 +34,7 @@ func (r *ServiceRuntime[T]) Config() *Config { return r.core.Config() }
 // ServiceStartup runs OnStart for all registered services that have one.
 func (c *Core) ServiceStartup(ctx context.Context, options any) Result {
 	c.shutdown.Store(false)
+	c.ctx, c.cancel = context.WithCancel(ctx)
 	startables := c.Startables()
 	if startables.OK {
 		for _, s := range startables.Value.([]*Service) {
@@ -53,11 +54,10 @@ func (c *Core) ServiceStartup(ctx context.Context, options any) Result {
 // ServiceShutdown drains background tasks, then stops all registered services.
 func (c *Core) ServiceShutdown(ctx context.Context) Result {
 	c.shutdown.Store(true)
+	c.cancel() // signal all context-aware tasks to stop
 	c.ACTION(ActionServiceShutdown{})
 
 	// Drain background tasks before stopping services.
-	// On timeout, the waiter goroutine persists until tasks complete —
-	// this is inherent to sync.WaitGroup (no cancel mechanism).
 	done := make(chan struct{})
 	go func() {
 		c.wg.Wait()