refactor(runtime): collapse speculative portability layers

Remove the one-consumer bounded-read primitive and shared terminal lifecycle controller, make terminal cleanup one awaited provider operation, and reuse one Code Runtime contract suite. Keep only reproduced cancellation and policy fixes; defer unproven replacement, prompt-attribution, and streaming-frame concerns to scoped markers.

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

@@ -14,16 +14,16 @@ Ordinary pipes do not cover one requirement. A persistent terminal needs PTY all
 
 `ctx.fs` and `ctx.subprocess` together define one execution world. Providers mounted together must describe the same path namespace, executables, processes, and terminal sessions; higher capabilities consume those two interfaces rather than name the provider.
 
-The filesystem interface owns the path facts that another capability needs without exposing its opaque target identity: a canonical process path, canonical `file:` URI, containment, and a bounded stable-handle text read. The existing text and mutation operations remain filesystem-owned.
+The filesystem interface owns the path facts that another capability needs without exposing its opaque target identity: a canonical process path, canonical `file:` URI, and containment. Existing whole and streaming text operations remain filesystem-owned; protocol consumers enforce their own retention limits while consuming the stream.
 
-The subprocess interface owns the process coordinates and primitives: canonical cwd, private runtime storage, executable lookup, ordinary raw or collected process spawning, and `spawnTerminal()`. The terminal operation is one deep primitive whose handle owns byte I/O, foreground groups, signalling, TERM-to-KILL session cleanup, and a quiescence wait. The interface package also exports a provider-neutral lifecycle controller that joins top-level settlement, lifetime cancellation, retryable provider cleanup, and bounded quiescence observation; each implementation supplies only its session-cleanup transaction. Prompt detection, idle inference, scrollback, sandbox policy, and owner lifecycle remain in the PTY consumer.
+The subprocess interface owns the process coordinates and primitives: canonical cwd, private runtime storage, executable lookup, ordinary raw or collected process spawning, and `spawnTerminal()`. The terminal operation is one deep primitive whose handle owns text I/O, foreground groups, signalling, and one awaited TERM-to-KILL operation that settles in-flight handle calls and reaches whole-session quiescence. Its signal cancels allocation only; the published handle owns its lifetime. Prompt detection, idle inference, scrollback, sandbox policy, and owner lifecycle remain in the PTY consumer.
 
 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 carries provider-owned file URIs through initialization and result rendering. One provider-lifetime signal aborts filesystem and protocol work during disposal, including workspace lookup before queue ownership; its JSON-RPC, pooling, synchronization, 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. The allocation signal is detached before publication, while readiness initialization retains setup cancellation. Prompt and silence evidence collected during asynchronous pre-write inspection is discarded when the provider write begins. Cancellation retains the send reservation until asynchronous foreground signalling settles, so the signal cannot target a successor; if a signaled send returns `inferred_idle` before its prompt arrives, that marker remains attributed to the prior send instead of settling a successor after its echo. A timed-out asynchronous write, or a signal failure during that write, retains the reservation until the provider settles the write. Completion of a stale inspection resumes polling for the current send. Close rejects new public signals after shutdown begins and drains public signals already in flight before returning.
-- `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 raw subprocess pipes carry newline-delimited UTF-8 JSON without a redundant base64 representation. 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. Prompt and silence evidence collected during asynchronous pre-write inspection is discarded when the provider write begins. Cancellation retains the send reservation while an in-flight write settles and then signals the foreground group, so late bytes or the signal cannot target a successor; a rejected write sends no signal. The absolute deadline remains armed throughout cancellation. A signal failure becomes terminal transport failure. Completion of a stale inspection resumes polling for the current send. Close rejects new public signals and delegates complete-session quiescence to the handle's awaited termination operation.
+- `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. The fixed runner is adapter-owned infrastructure below `ctx.subprocess.runtimeRoot`, so its write carries an explicit `danger-full-access` policy instead of inheriting the model-facing filesystem mode. 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 forwarding, and raw subprocess pipes carry newline-delimited UTF-8 JSON without a redundant base64 representation. 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.
 
@@ -35,6 +35,10 @@ Generic consumers use that execution world:
 
 **Move PTY readiness and session policy into the subprocess service.** Rejected because those are persistent-terminal consumer semantics, not OS process mechanics. A subprocess provider owns what only its substrate can do; `dsh-pty-local` owns what a Harness terminal means.
 
+**Expose separate terminal termination and quiescence operations plus a shared lifecycle controller.** Rejected because every terminal consumer needs the same single cleanup outcome. Separate operations export provider bookkeeping, bounded-observer, and retry semantics without a production consumer; one awaited provider operation is a deeper interface.
+
+**Add a stable bounded-read primitive to the filesystem seam.** Rejected because only LSP needs a complete-document byte ceiling, which it can enforce while consuming the existing text stream. A second primitive forces every provider to implement stable-handle and no-follow mechanics, including a remote helper protocol, without an observed concurrent-replacement defect.
+
 **Delete the worker-thread Code Runtime.** Rejected because portability does not erase its current deployment need. The subprocess backend requires a Node executable and filesystem materialization; the worker backend has neither requirement and remains the supported single-process path.
 
 **Run the whole harness inside the remote environment.** Rejected as a different deployment model. Making execution capabilities portable does not move model calls, session state, plugin state, or the agent loop.