refactor(process): split the process manager out of the bash executor

New process/ capability family: @deepseek-ai/dsh-process owns ctx.processes —
abstract ProcessManager.spawn(spec) over a fully-explicit ProcessSpawnSpec —
plus the shared DSH_* managed-environment and CollectedOutput vocabulary;
@deepseek-ai/dsh-process-local carries the former bash-local run.ts plumbing
(detached groups, tail-keep spill-backed output, credential scrub, kill
escalation, kill-and-join disposal) with no config of its own.

dsh-bash-local becomes a consumer: it keeps command defaulting, the fused
deadline timedOut/aborted classification, the model-friendly terminal env
(now merged through the ordinary env channel), and the [stderr]-marked
background read merge, and spawns through ctx.processes. Background-process
lifetime moves to the manager, so an executor reload no longer kills live
background work; a background spawn failure is injected once into the read
path instead of being buffered as fake stderr. dsh-bash re-exports the moved
vocabulary so bash consumers keep one import root; dsh-bash-sandbox only
redeclares the inherited inject.

Every composition loading a bash executor now loads dsh-process-local (CLI,
examples, python bundled runtime, create-sdk bash feature, inline test
configs).

packages/bash/bash-local/README.md

@@ -1,8 +1,8 @@
 # @deepseek-ai/dsh-bash-local
 
-Local-subprocess implementation of the `@deepseek-ai/dsh-bash` executor seam: `LocalBashExecutor` spawns `bash -c <command>` per call in its own process group, collects bounded output with size-limited full-stream spill files, and escalates kills SIGTERM→SIGKILL across the whole group.
+Local implementation of the `@deepseek-ai/dsh-bash` executor seam over the [`@deepseek-ai/dsh-process`](../../process/process/README.md) manager: `LocalBashExecutor` spawns `bash -c <command>` per call as a managed process group through `ctx.processes`, and owns everything bash-shaped — command defaulting and caps, timeout/cancel classification, the model-friendly terminal environment, and the model-facing stdout/stderr merge for background reads. Group mechanics (bounded spill-backed output, credential scrub, kill escalation, disposal) are the process manager's.
 
-The package root exports the default and named `LocalBashExecutor` plugin plus its `Config`; subprocess plumbing stays internal to the implementation package.
+The package root exports the default and named `LocalBashExecutor` plugin plus its `Config`.
 
 ## Config
 
@@ -22,11 +22,11 @@ The package root exports the default and named `LocalBashExecutor` plugin plus i
 
 Design surveyed against the bash tools of Claude Code, OpenCode, Codex, and pi; the notable choices:
 
-- **Spawn per call, no shell state** — every call is a fresh non-login `bash -c` (deterministic; no rc files). All four surveyed tools spawn per call. `XXX(stateful-shell)` in `src/run.ts` records the two proven stateful designs (Claude Code's cwd-only persistence; Codex's PTY exec sessions) for when real workflows demand them.
-- **Process-group kills with escalation** — children are spawned `detached` (own process group); kills send SIGTERM to the group, then SIGKILL after the `graceMs` grace (default 3s — OpenCode's escalation; pipelines and subshells die with the parent). After the main shell exits, inherited stdout/stderr pipes receive the same bounded drain grace so a surviving descendant cannot hold the command open indefinitely. ESRCH is tolerated; daemons that re-parent away from the group can still survive — same caveat as the surveyed tools.
-- **Tail-keep truncation + bounded spill files** — output beyond `maxOutputBytes` keeps the in-memory TAIL (errors/results cluster at the end — pi/OpenCode rationale) while the FULL stream is appended to a temp file whose path is reported when available. A foreground `BashExecRequest.stdoutMaxBytes` can raise stdout's capture budget for one trusted caller; stderr and background tasks still use `maxOutputBytes`. A stream larger than `maxSpillBytes` discards its now-incomplete spill and returns only the marked truncated tail. If the final spill close reports a delayed writeback failure, the executor likewise withholds the path rather than advertising an incomplete file.
-- **Model-friendly env + credential scrub** — `process.env` minus credential-shaped vars (`*KEY*`/`*SECRET*`/`*TOKEN*`) and all ambient `DSH_*` names, then `NO_COLOR=1 TERM=dumb PAGER=cat GIT_PAGER=cat` (Codex's hardcoded set) so pagers and ANSI color don't garble results. A spec's ordinary `env` is merged after the scrub but rejects `DSH_*`; managed `dshEnv` rejects ordinary names and merges last, preventing stale nested-harness identity. Supplied stdin is written and closed; otherwise fd 0 is `/dev/null`. See the [stdin/env Agent Note](../../../.agents/notes/implemented/architecture/2026-06-30-bash-stdin-env-trusted-plugin-surface.md) and [managed environment Agent Note](../../../.agents/notes/implemented/feature/2026-07-10-agent-session-identity-and-log-location.md).
-- **Background processes** — `start()` returns a live `BashProcess` handle immediately, no timeout applies (Claude Code detaches timeouts when backgrounding), the handle's `readOutput()` is incremental with whole-stream byte offsets, and disposal kills every running process and awaits its exit. Everything task-shaped (ids, ownership, polling, notices) lives in the generic [`ctx.tasks` runtime](../../tasks/tasks/README.md), which the tool layer registers the handle with — this executor never sees a session or a registry.
+- **Spawn per call, no shell state** — every call is a fresh non-login `bash -c` (deterministic; no rc files). All four surveyed tools spawn per call. `XXX(stateful-shell)` in `src/index.ts` records the two proven stateful designs (Claude Code's cwd-only persistence; Codex's PTY exec sessions) for when real workflows demand them.
+- **Configured budgets over managed groups** — `resolve()` fills `workdir`/`timeoutMs`/`stdoutMaxBytes` from config, and every spawn hands the manager explicit byte caps, spill cap, and `graceMs` (default 3s — OpenCode's escalation). Process-group kills, the post-exit pipe-drain grace, tail-keep truncation, and bounded spill files are [`dsh-process-local`](../../process/process-local/README.md) mechanics. A foreground `BashExecRequest.stdoutMaxBytes` can raise stdout's capture budget for one trusted caller; stderr and background runs still use `maxOutputBytes`.
+- **Timeout and cancel classification** — `run()` fuses its config-clamped timeout with the caller's signal through one deadline; only the executor's own timeout reports `timedOut`, an upstream cancel reports `aborted`, and a self-signaled command reports neither ([timeout-library Agent Note](../../../.agents/notes/implemented/architecture/2026-07-06-timeout-deadline-library.md)).
+- **Model-friendly terminal env** — `NO_COLOR=1 TERM=dumb PAGER=cat GIT_PAGER=cat` (Codex's hardcoded set) so pagers and ANSI color don't garble results, merged as ordinary env under the manager's credential scrub and `DSH_*` channel rules; an explicit caller entry still wins. See the [stdin/env Agent Note](../../../.agents/notes/implemented/architecture/2026-06-30-bash-stdin-env-trusted-plugin-surface.md) and [managed environment Agent Note](../../../.agents/notes/implemented/feature/2026-07-10-agent-session-identity-and-log-location.md).
+- **Background processes** — `start()` returns a live `BashProcess` handle immediately, no timeout applies (Claude Code detaches timeouts when backgrounding), and the handle's `readOutput()` merges the manager's offset-based stdout/stderr reads into one marked-section delta with a consuming cursor. A still-running process belongs to the manager, so it survives executor reloads and dies (killed and joined) with the manager's disposal. Everything task-shaped (ids, ownership, polling, notices) lives in the generic [`ctx.tasks` runtime](../../tasks/tasks/README.md), which the tool layer registers the handle with — this executor never sees a session or a registry.
 
 ## Model Experience
 
@@ -40,8 +40,7 @@ No direct invalidation; the named consumer owns any request-prefix changes.
 
 - **Unconfined by itself** — this executor always runs commands with the harness process's authority; deployments needing confinement compose [`dsh-bash-sandbox`](../bash-sandbox/README.md), while per-call allow/deny/ask policy belongs on `tools/pre-execute`.
 - **No persistent shell or PTY** — every call starts a fresh non-login `bash -c`; cwd-only persistence and interactive terminal sessions remain deferred until a real workflow requires them.
-- **POSIX-only** — the `bash` binary, detached process groups, group kills, and SIGTERM→SIGKILL escalation are hardcoded; Windows is unsupported.
-- **The credential scrub is a name heuristic** — `*KEY*`/`*SECRET*`/`*TOKEN*` only; differently-named secrets (e.g. `*PASSWORD*`) pass through, and a whitelist for over-scrubbed vars is noted future work.
-- **Completed spill files are not deleted** — bounded full-output recovery files (and the private per-process spill dir) accumulate under the OS tmpdir until something external cleans them; oversize incomplete spills are discarded and deletion is attempted immediately, but a cleanup failure can leave a bounded file behind.
+- **POSIX-only** — the `bash` binary is hardcoded, and the underlying manager's group semantics are POSIX; Windows is unsupported.
+- **A background spawn-failure note is single-delivery** — the manager buffers no output for a process that never ran, so the executor injects `spawn failed: …` into exactly one `readOutput()` delta; a reader that discards that delta cannot recover it.
 
-The raw process handling lives in `src/run.ts`; `src/index.ts` is the service wiring.
+Scrub-heuristic and spill-retention caveats live with [`dsh-process-local`](../../process/process-local/README.md), which owns those mechanics.