Merge refreshed rfc/pty into feature/persistent-pty-sessions

# Conflicts:
#	docs/architecture.md
#	docs/capability-seams.md
#	docs/config-catalog.md
#	docs/cordis-catalog/services.md
#	docs/module-graph.md
#	docs/tool-catalog.md
#	examples/acp-agent/tests/acp.snapshot.ts
#	examples/headless-agent/tests/headless.snapshot.ts
#	examples/package.json
#	packages/README.md
#	packages/cordis/tool-cordis/src/api-catalog.ts
#	packages/core/tools/tests/gen-tool-catalog.spec.ts
#	pnpm-lock.yaml
#	pnpm-workspace.yaml
#	scripts/gen-tool-catalog.ts
#	scripts/type-equiv.manifest.json
#	website/.vitepress/config/api-sidebar.json

packages/pty/pty-local/src/invariant.ts

@@ -0,0 +1,30 @@
+/**
+ * Package-owned invariant companion for `@deepseek-ai/dsh-pty-local`.
+ * @module @deepseek-ai/dsh-pty-local/invariant
+ */
+
+/* jscpd:ignore-start */
+import type { Context } from 'cordis'
+import type { InvariantInstaller } from '@deepseek-ai/dsh-invariants'
+
+const PACKAGE_NAME = '@deepseek-ai/dsh-pty-local'
+
+/** Cordis companion plugin name. */
+export const name = 'pty-local-invariant'
+/** Service required before the companion can reserve package ownership. */
+export const inject = ['invariants']
+
+/**
+ * No runtime invariant: readiness, terminal buffers, and process-tree state are private per-session
+ * implementation state, and the backend publishes no independent lifecycle stream or snapshot.
+ */
+const install: InvariantInstaller = () => {}
+
+/**
+ * Register this package's invariant companion.
+ * @param ctx - Cordis context carrying the invariant service.
+ * @returns the installed registration's disposer after setup succeeds.
+ */
+export const apply = (ctx: Context): Promise<() => void> =>
+  Promise.resolve(ctx.invariants.register(PACKAGE_NAME, install))
+/* jscpd:ignore-end */