fix(spec): the specVersion refusal prescribes the current protocol range, spelled from PROTOCOL_MAJOR

ManifestSchema's guidance for a manifest that writes specVersion told the
author to declare engines: { protocol: '^17' } (the range the scaffold
stamps). At protocol 18 os init stamps '^18' and the load-time handshake
refuses '^17', so following the prescription produced a manifest the
runtime refuses to load. The card's sweep missed it because the quotes
are backslash-escaped. The range is now spelled from PROTOCOL_MAJOR, so
it moves with the handshake it names. manifest-unknown-keys.test.ts pins
that the prescribed range is the current major and not the previous one.

Claude-Session: https://claude.ai/code/session_01VZqqwTj2wsihZEbfT6yyYN
Co-authored-by: Claude <noreply@anthropic.com>

Author: claude

packages/spec/src/kernel/manifest-unknown-keys.test.ts

@@ -38,6 +38,7 @@
 import { describe, it, expect } from 'vitest';
 
 import { ManifestSchema, PluginEnginesSchema } from './manifest.zod';
+import { PROTOCOL_MAJOR } from './protocol-version';
 import { ArtifactPackageSchema, ObjectStackDefinitionSchema } from '../stack.zod';
 import { formatZodError } from '../shared/error-map.zod';
 
@@ -104,6 +105,10 @@ describe("unknown keys inside `manifest:` are refused at parse (the silent-drop
     const issue = unrecognized(result)!;
     expect(issue.keys).toEqual(['specVersion']);
     expect(issue.message).toContain('engines.protocol');
+    // The range it prescribes is the one the handshake admits: the current
+    // protocol major, never the previous one the handshake refuses.
+    expect(issue.message).toContain(`protocol: '^${PROTOCOL_MAJOR}'`);
+    expect(issue.message).not.toContain(`protocol: '^${PROTOCOL_MAJOR - 1}'`);
     expect(issue.message).not.toContain('Did you mean');
   });
 });

packages/spec/src/kernel/manifest.zod.ts

@@ -2,6 +2,7 @@
 
 import { z } from 'zod';
 import { CORE_PLUGIN_TYPES } from './plugin.zod';
+import { PROTOCOL_MAJOR } from './protocol-version';
 import { SEMVER_2_0_0_VERSION_PATTERN } from './version-grammar';
 import { retiredKey } from '../shared/retired-key';
 import { closedObject, strictObject, strictObjectError } from '../shared/strict-object';
@@ -407,9 +408,12 @@ export const ManifestSchema = strictObject({
     + 'exiting 0. The declared keys are enumerated by `ManifestSchema` (@objectstack/spec, '
     + 'kernel/manifest.zod.ts) and in the package-manifest reference docs.',
   guidance: {
+    // The prescribed range is spelled from PROTOCOL_MAJOR, the value the load-time
+    // handshake compares and `os init` stamps, so it moves with the protocol instead
+    // of naming a major the handshake already refuses.
     specVersion:
       '`specVersion` is not a package-manifest key. The protocol axis the runtime checks at '
-      + 'load is `engines.protocol` — declare `engines: { protocol: \'^17\' }` (the range the '
+      + `load is \`engines.protocol\` — declare \`engines: { protocol: '^${PROTOCOL_MAJOR}' }\` (the range the `
       + 'scaffold stamps); `specVersion` keeps its meaning only on the marketplace TEMPLATE '
       + 'manifest (`cloud/template-manifest.zod.ts`), which is a different surface.',
   },