feat: declare module permissions

Establishes the one canonical PermissionDeclaration contract
(packages/contracts/src/authorization.ts) — id/baseline/description,
strict, unknown-property-rejecting — consumed by both Core's
authorization registry and module manifests, replacing Core's
previously separate interface.

Bumps the canonical module manifest to manifestVersion 3: permissions
become complete declarations instead of bare identifier strings, with
manifest-owned namespace and duplicate-id enforcement. Version 2 and
bare string-array permissions are rejected outright; there is no
compatibility adapter.

Adds composePlatformPermissionRegistry (core/src/modules/permissions.ts),
a pure, synchronous composer that builds one platform permission
registry from Core's own declarations plus every already-discovered
module's, in deterministic order, reusing createPermissionRegistry
and rejecting any module-contributed permission in the reserved
core.* namespace. core/src/authorization remains independent of
core/src/modules; only the module integration layer depends on
authorization.

Updates the module template, module-development docs, authorization
docs, and existing manifest fixtures for manifestVersion 3. Does not
wire the combined registry into apps/api — that is pass 2.

core/src/modules/permissions.ts

@@ -0,0 +1,73 @@
+import {
+  CORE_PERMISSION_DECLARATIONS,
+  createPermissionRegistry,
+  type PermissionDeclaration,
+  type PermissionRegistry,
+} from "../authorization/index.js";
+import type { DiscoveredModule } from "./discovery.js";
+
+const CORE_PERMISSION_NAMESPACE_PREFIX = "core.";
+
+export type ModulePermissionCompositionErrorCode = "MODULE_PERMISSION_RESERVED_NAMESPACE";
+
+/** Thrown only at composition time, never per-request. Carries the offending module and
+ * permission id deliberately — like `PermissionRegistryError`, this is a startup-time
+ * configuration error, not a runtime response, and neither value is sensitive. Never carries a
+ * module directory, manifest path, caught error, or stack detail. */
+export class ModulePermissionCompositionError extends Error {
+  readonly code: ModulePermissionCompositionErrorCode;
+  readonly moduleId: string;
+  readonly permissionId: string;
+
+  constructor(moduleId: string, permissionId: string) {
+    super(
+      `Module "${moduleId}" cannot declare permission "${permissionId}": the "core." namespace is reserved for Core's own permissions.`,
+    );
+    this.name = "ModulePermissionCompositionError";
+    this.code = "MODULE_PERMISSION_RESERVED_NAMESPACE";
+    this.moduleId = moduleId;
+    this.permissionId = permissionId;
+    this.stack = `${this.name}: ${this.message}`;
+    Object.freeze(this);
+  }
+}
+
+/**
+ * Core's module-integration-layer composition helper: builds the one platform permission
+ * registry from Core's own declarations (`CORE_PERMISSION_DECLARATIONS`) plus every already
+ * discovered module's manifest-declared permissions. Deliberately lives in `core/src/modules`,
+ * not `core/src/authorization` — the dependency runs one way only, this layer depends on
+ * authorization's `createPermissionRegistry`, and authorization never imports module discovery
+ * or runtime. This is pure, synchronous, in-memory composition over already-discovered,
+ * already-validated data: no filesystem, environment, database, network, or module-code
+ * execution happens here, and the caller (not this function) is responsible for having already
+ * produced a complete, successfully discovered module list (for example via `discoverModules`).
+ *
+ * Declaration order is deterministic and meaningful for duplicate detection: Core's own
+ * declarations first, then each module in the exact order it appears in `modules`, and within a
+ * module its declarations in manifest-array order. Duplicate exact permission ids — including a
+ * module colliding with a Core-owned id or with another module's — fail via the same
+ * `PermissionRegistryError` `createPermissionRegistry` already throws for any duplicate; this
+ * function does not reimplement or duplicate that detection.
+ *
+ * `core.*` is reserved for Core's own permissions. A discovered module contributing any
+ * `core.`-prefixed permission id — regardless of that module's own id, and regardless of whether
+ * it happens to exactly collide with an existing declaration — fails composition with
+ * `ModulePermissionCompositionError` rather than silently registering or silently colliding.
+ */
+export function composePlatformPermissionRegistry(
+  modules: readonly DiscoveredModule[],
+): PermissionRegistry {
+  const declarations: PermissionDeclaration[] = [...CORE_PERMISSION_DECLARATIONS];
+
+  for (const module of modules) {
+    for (const declaration of module.manifest.permissions) {
+      if (declaration.id.startsWith(CORE_PERMISSION_NAMESPACE_PREFIX)) {
+        throw new ModulePermissionCompositionError(module.manifest.id, declaration.id);
+      }
+      declarations.push(declaration);
+    }
+  }
+
+  return createPermissionRegistry(declarations);
+}