Phase 15: snapshots, forks, export/import, cognitive replay, experiments

- snapshots: checksummed JSON archive of every mind-scoped state table plus
  identity/personality/config and the event position; stored, downloadable
- fork: restore into a new mind with all ids remapped; event references are
  kept so history before the fork is shared by reference
- export/import: same archive; import is hostile-input validated (size,
  allow-listed tables, row caps, column names, checksum, forced mind_id)
- compare: deterministic counts, belief diffs by proposition, personality
  and config diffs, event mix
- replay: Runtime.Step for synchronous drivers; sandbox fork driven one
  stimulus at a time under a forbidden capability context; recorded model
  responses via a replaying router; steps labelled exact / approximate /
  diverged with recorded-vs-replayed digests
- experiments: definition (overrides, stimuli, expectations, seed, duration),
  background run in a disabled subject mind, stored and exportable results
- migration 0015, API, UI (Snapshots and Replay tabs, Experiments section,
  compare page), noemactl snapshots/compare/replay/experiments, docs

internal/app/app.go

@@ -20,6 +20,7 @@ import (
 	"github.com/andydixon/noema/internal/conversation"
 	"github.com/andydixon/noema/internal/dreaming"
 	"github.com/andydixon/noema/internal/events"
+	"github.com/andydixon/noema/internal/experiments"
 	"github.com/andydixon/noema/internal/goals"
 	"github.com/andydixon/noema/internal/graph"
 	"github.com/andydixon/noema/internal/integrations"
@@ -33,7 +34,9 @@ import (
 	"github.com/andydixon/noema/internal/observability"
 	"github.com/andydixon/noema/internal/predictions"
 	"github.com/andydixon/noema/internal/reflection"
+	"github.com/andydixon/noema/internal/replay"
 	"github.com/andydixon/noema/internal/security/secrets"
+	"github.com/andydixon/noema/internal/snapshots"
 )
 
 // Deps is everything a handler may need. Fields are added per phase.
@@ -62,6 +65,9 @@ type Deps struct {
 	Capabilities  *capabilities.Service
 	Integrations  *integrations.Manager
 	Dreaming      *dreaming.Service
+	Snapshots     *snapshots.Store
+	Replay        *replay.Service
+	Experiments   *experiments.Service
 	LLM           *router.Router
 	LLMStore      *router.Store
 	Prompts       *prompts.Store