feat(schema-form): schema-driven React form renderer package

@deepseek-ai/dsh-client-schema-form rehydrates the wire's serialized
schemastery envelope (new Schema(json)) and edits a draft user section
against it: presence-in-draft marks a field overridden with a per-field
reset, inherited values render as placeholders, role('secret') slots are
write-only with configured-state placeholders from the wire's secrets
list, dict adds take a union-typed sKey as their vocabulary, and any
node the renderer cannot faithfully edit falls back to a read-only view
instead of silently disappearing. renderField(context) is the role hook
the Models page will use for the credential-ref control; validateDraft
runs the same rehydrated validator the host uses, so the browser and
host judge one schema.

packages/client/schema-form/tests/invariant.spec.ts

@@ -0,0 +1,12 @@
+import { describe, expect, it } from 'vitest'
+import { Context } from 'cordis'
+import * as SchemaFormInvariant from '@deepseek-ai/dsh-client-schema-form/invariant'
+import InvariantService from '@deepseek-ai/dsh-invariants'
+
+describe('invariant companion', () => {
+  it('registers under the package name with an empty installer', async () => {
+    const ctx = new Context()
+    await ctx.plugin(InvariantService, { enabled: true })
+    await expect(ctx.plugin(SchemaFormInvariant).await()).resolves.toBeDefined()
+  })
+})