fix(runtime): close lifecycle teardown races

.agents/notes/implemented/architecture/2026-07-28-portable-execution-world-consumers.md

@@ -22,8 +22,8 @@ Generic consumers use that execution world:
 
 - `dsh-bash-local` continues to map Bash semantics onto ordinary `ctx.subprocess.spawn()`.
 - `dsh-lsp-local` reads and contains source through `ctx.fs`, resolves and launches language servers through `ctx.subprocess`, and sends provider-owned file URIs. Its JSON-RPC, pooling, synchronization, cancellation, and normalization stay unchanged.
-- `dsh-pty-local` maps persistent-shell semantics onto `ctx.subprocess.spawnTerminal()`. The local `node-pty` and process-inspection implementation moves into `dsh-subprocess-local`; another subprocess provider supplies the same primitive. A timed-out asynchronous write retains the send reservation until the provider settles it, and completion of a stale inspection resumes polling for the current send.
-- `dsh-code-runtime-subprocess` materializes a dependency-free runner through `ctx.fs` and launches it through `ctx.subprocess`, preserving the Code Runtime binding and output contract across local or remote worlds. It shares host-side worker mechanics through the non-plugin `dsh-code-runtime-worker/runtime-host` subpath instead of copying them. The heap-bounded worker rejects oversized binding frames before transfer, each outer hop enforces the same bound before serialization, and the launcher publishes an accepted terminal frame before reaping its controller so a descendant that inherits controller pipes cannot suppress completion; the host still awaits process-group quiescence.
+- `dsh-pty-local` maps persistent-shell semantics onto `ctx.subprocess.spawnTerminal()`. The local `node-pty` and process-inspection implementation moves into `dsh-subprocess-local`; another subprocess provider supplies the same primitive. The allocation signal is detached before publication, while readiness initialization retains setup cancellation. A timed-out asynchronous write, or a cancellation whose foreground signal fails during that write, retains the send reservation until the provider settles it; completion of a stale inspection resumes polling for the current send.
+- `dsh-code-runtime-subprocess` materializes a dependency-free runner through `ctx.fs` and launches it through `ctx.subprocess`, preserving the Code Runtime binding and output contract across local or remote worlds. It shares host-side worker mechanics through the non-plugin `dsh-code-runtime-worker/runtime-host` subpath instead of copying them. Preparation carries one lifecycle signal through filesystem resolution, materialization, and executable lookup so disposal can abort a stalled provider. The heap-bounded worker rejects oversized binding frames before transfer, each outer hop enforces the same bound before serialization, and the launcher publishes an accepted terminal frame before reaping its controller so a descendant that inherits controller pipes cannot suppress completion; the host still awaits process-group quiescence.
 
 `dsh-code-runtime-worker` remains a separate implementation. It is the smaller in-process backend and works in single-file distributions that cannot assume an installed Node executable. Remote filesystem/process compositions select `dsh-code-runtime-subprocess`; they do not need a provider-specific Code Runtime package.
 
@@ -45,4 +45,4 @@ A remote execution provider implements only its shared sandbox owner plus filesy
 
 The fundamental interfaces are wider, and a filesystem/subprocess pair must agree on one execution world. The added operations are limited to facts and lifecycle mechanics that current generic consumers require; model schemas, protocol framing, readiness policy, and presentation do not leak into the providers.
 
-The local implementation absorbs `node-pty` and platform process inspection because it owns local terminal mechanics. This moves code without weakening terminal teardown: disposal still waits for exact PID-identity-fenced descendants and the top-level terminal process to reach quiescence.
+The local implementation absorbs `node-pty` and platform process inspection because it owns local terminal mechanics. This moves code without weakening terminal teardown: disposal waits for exact PID-identity-fenced descendants retained during foreground inspection, Linux session members that survive top-level exit, and the top-level terminal process to reach quiescence. macOS cannot enumerate a POSIX session after its leader exits, so a child that reparents between inspection snapshots remains an explicit local-provider limitation rather than a reason to move process mechanics back into the PTY consumer.