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/tool-pty/src/index.ts

@@ -125,7 +125,6 @@ export function apply(ctx: Context): void {
       if (args.run_in_background === true) {
         const tasks = ctx.get('tasks')
         if (tasks === undefined) throw new Error('background terminal sends require @deepseek-ai/dsh-tasks and @deepseek-ai/dsh-tool-tasks')
-        if (exec.signal?.aborted === true) throw new Error('terminal send aborted')
         let cancelRequested = false
         const taskId = tasks.start({
           kind: 'pty-send',
@@ -148,9 +147,9 @@ export function apply(ctx: Context): void {
         })
         return { content: textResult(`started background task ${taskId}`), isError: false }
       }
-      const operation = ctx.pty.startSend(owner, id, { ...request, ...exec.signal ? { signal: exec.signal } : {} })
+      const operation = ctx.pty.startSend(owner, id, { ...request, signal: exec.signal })
       const result = await operation.done
-      if (exec.signal?.aborted === true) throw new Error('terminal send aborted')
+      if (exec.signal.aborted) throw new Error('terminal send aborted')
       return { content: textResult(renderSend(result)), isError: false, meta: result }
     },
     presentCall(args) {

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

@@ -0,0 +1,30 @@
+/**
+ * Package-owned invariant companion for `@deepseek-ai/dsh-tool-pty`.
+ * @module @deepseek-ai/dsh-tool-pty/invariant
+ */
+
+/* jscpd:ignore-start */
+import type { Context } from 'cordis'
+import type { InvariantInstaller } from '@deepseek-ai/dsh-invariants'
+
+const PACKAGE_NAME = '@deepseek-ai/dsh-tool-pty'
+
+/** Cordis companion plugin name. */
+export const name = 'tool-pty-invariant'
+/** Service required before the companion can reserve package ownership. */
+export const inject = ['invariants']
+
+/**
+ * No runtime invariant: this stateless adapter contributes tools and prompt guidance, while PTY
+ * lifecycle and background-task relationships remain owned by the services it composes.
+ */
+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 */