docs(spec): cli-extension Discover step says what loads an oclif plugin into os

The module TSDoc's step 2 said @objectstack/cli lists the plugin in its
oclif.plugins array, or that users install it with `os plugins install`.
@objectstack/cli declares no oclif.plugins and ships no plugin manager, so
neither is true. The step now names the oclif rule (oclif.plugins plus
dependencies of the CLI's own package.json) and the os-distribution route.

Claude-Session: https://claude.ai/code/session_01UtnxvdiN376GF3sgXwAw4d
Co-authored-by: Claude <noreply@anthropic.com>

Author: claude

.changeset/21286-cli-extension-tsdoc-discover.md

@@ -0,0 +1,9 @@
+---
+'@objectstack/spec': patch
+---
+
+The `kernel/cli-extension` module documentation no longer tells plugin authors to run `os plugins install`. Step 2, "Discover", said the plugin is listed in `@objectstack/cli`'s `oclif.plugins` array, or that users install it with `os plugins install`. Neither is true: `@objectstack/cli` declares no `oclif.plugins` and ships no plugin manager, so `os plugins` is not a command. The step now says what loads a plugin: oclif loads a plugin that the CLI's own `package.json` lists in both `oclif.plugins` and `dependencies`. To add a plugin's commands to `os`, build an `os` distribution whose own `package.json` lists the plugin in both places. The generated reference page carries the same text.
+
+Clause-②: no
+
+Documentation only. No schema, export or type changes.

packages/spec/src/kernel/cli-extension.zod.ts

@@ -14,8 +14,11 @@ import { z } from 'zod';
  * 
  * 1. **Declare** — Plugin's `package.json` includes an `oclif` config section
  *    declaring its commands directory and any topics.
- * 2. **Discover** — The main CLI (`@objectstack/cli`) lists the plugin in its
- *    `oclif.plugins` array, or users install it via `os plugins install <pkg>`.
+ * 2. **Discover** — oclif loads a plugin that the CLI's own `package.json`
+ *    lists in both `oclif.plugins` and `dependencies`. `@objectstack/cli`
+ *    lists none and ships no plugin manager, so `os plugins` is not a
+ *    command. To add a plugin's commands to `os`, build an `os` distribution:
+ *    a package whose own `package.json` lists the plugin in both places.
  * 3. **Load** — oclif automatically discovers and registers all Command classes
  *    exported from the plugin's commands directory.
  *