Feat v0.8.0 files sandbox module

Bridge ObjectStore (PVC/S3) into the Starlark sandbox with extension-scoped
key namespacing. New files module with put/get/meta/list/delete/exists
builtins gated by files.read and files.write permissions.

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

server/sandbox/runner.go

@@ -33,6 +33,7 @@ import (
 	"armature/events"
 	"armature/metrics"
 	"armature/models"
+	"armature/storage"
 	"armature/store"
 )
 
@@ -77,6 +78,7 @@ type Runner struct {
 	dbPostgres      bool                 // true = use $N placeholders; false = use ?
 	allowPrivateIPs bool
 	bus             *events.Bus
+	objectStore     storage.ObjectStore  // nil = files module unavailable
 }
 
 // NewRunner creates a runner with the given sandbox and dependencies.
@@ -116,6 +118,11 @@ func (r *Runner) SetBus(bus *events.Bus) {
 	r.bus = bus
 }
 
+// SetObjectStore attaches the blob storage backend for the files module.
+func (r *Runner) SetObjectStore(s storage.ObjectStore) {
+	r.objectStore = s
+}
+
 // SetAllowPrivateIPs disables the SSRF check that blocks connections to
 // private/loopback IPs. For self-hosted environments where extensions
 // reach internal services. Controlled by EXT_ALLOW_PRIVATE_IPS env var.
@@ -336,8 +343,9 @@ func (r *Runner) buildModulesWithLibCtx(ctx context.Context, packageID string, m
 
 	modules := make(map[string]starlark.Value)
 
-	// Track db permission level: 0=none, 1=read, 2=write
+	// Track tiered permission levels: 0=none, 1=read, 2=write
 	dbLevel := 0
+	filesLevel := 0
 	hasBatchExec := false
 
 	for _, perm := range granted {
@@ -363,6 +371,14 @@ func (r *Runner) buildModulesWithLibCtx(ctx context.Context, packageID string, m
 		case models.ExtPermDBWrite:
 			dbLevel = 2
 
+		case models.ExtPermFilesRead:
+			if filesLevel < 1 {
+				filesLevel = 1
+			}
+
+		case models.ExtPermFilesWrite:
+			filesLevel = 2
+
 		case models.ExtPermWorkflowAccess:
 			modules["workflow"] = BuildWorkflowModule(ctx, r.stores)
 
@@ -391,6 +407,15 @@ func (r *Runner) buildModulesWithLibCtx(ctx context.Context, packageID string, m
 		})
 	}
 
+	// Wire files module at the highest granted level.
+	if filesLevel > 0 && r.objectStore != nil {
+		modules["files"] = BuildFilesModule(ctx, FilesModuleConfig{
+			PackageID: packageID,
+			CanWrite:  filesLevel == 2,
+			Store:     r.objectStore,
+		})
+	}
+
 	// A package reads its own admin + team + user settings.
 	userID := ""
 	teamID := ""