P1 (part 1): move skilltools core -> tool/ (clean, verbatim)

The tool registry core (registry, permission model, Invocation, gated-tool
wrapper, ssrf guard, hmac, encryption, argcoerce, helpers, rootrun,
session_tools, webhook_rate_limit) had zero mort coupling — it imports only
majordomo/llm + x/crypto/hkdf — so it moves verbatim with a package rename
(skilltools -> tool). All same-package tests came along and pass; the SSRF,
gated-wrapper, encryption and output-pattern invariants are re-anchored here.

majordomo re-enters the module graph (now pinned to the latest, incl. the
front-loaded-output fix). model/ + llmmeta + structured follow next.

Docs: CLAUDE.md now requires README/examples to stay in sync with changes in
the same commit; CI skips docs/example-only pushes via paths-ignore.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

tool/checks_test.go

@@ -0,0 +1,56 @@
+package tool
+
+import (
+	"strings"
+	"testing"
+)
+
+func TestCheckAuthoring_AllowsAnyone(t *testing.T) {
+	r := NewRegistry()
+	_ = r.Register(&fakeTool{name: "calc", perm: Permission{AuthoringRequirement: RequirementAnyone}})
+	if err := CheckAuthoring(r, []string{"calc"}, false); err != nil {
+		t.Fatalf("expected anyone to pass, got %v", err)
+	}
+}
+
+func TestCheckAuthoring_BlocksNonAdminFromAdminTool(t *testing.T) {
+	r := NewRegistry()
+	_ = r.Register(&fakeTool{name: "db_select", perm: Permission{AuthoringRequirement: RequirementAdmin}})
+	err := CheckAuthoring(r, []string{"db_select"}, false)
+	if err == nil || !strings.Contains(err.Error(), "requires admin authoring") {
+		t.Fatalf("expected admin-required error, got %v", err)
+	}
+}
+
+func TestCheckAuthoring_AllowsAdminWithAdminTool(t *testing.T) {
+	r := NewRegistry()
+	_ = r.Register(&fakeTool{name: "db_select", perm: Permission{AuthoringRequirement: RequirementAdmin}})
+	if err := CheckAuthoring(r, []string{"db_select"}, true); err != nil {
+		t.Fatalf("expected admin to pass, got %v", err)
+	}
+}
+
+func TestCheckAuthoring_UnknownTool(t *testing.T) {
+	r := NewRegistry()
+	err := CheckAuthoring(r, []string{"missing"}, true)
+	if err == nil || !strings.Contains(err.Error(), "unknown tool") {
+		t.Fatalf("expected unknown-tool error, got %v", err)
+	}
+}
+
+func TestCheckShareSafety_Pass(t *testing.T) {
+	r := NewRegistry()
+	_ = r.Register(&fakeTool{name: "search", perm: Permission{SafeForShare: true}})
+	if err := CheckShareSafety(r, []string{"search"}); err != nil {
+		t.Fatalf("expected safe tool to pass, got %v", err)
+	}
+}
+
+func TestCheckShareSafety_BlocksUnsafe(t *testing.T) {
+	r := NewRegistry()
+	_ = r.Register(&fakeTool{name: "balance", perm: Permission{SafeForShare: false}})
+	err := CheckShareSafety(r, []string{"balance"})
+	if err == nil || !strings.Contains(err.Error(), "operates on the caller's own data") {
+		t.Fatalf("expected share-safety error, got %v", err)
+	}
+}