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).

docs/cordis-catalog/services.md

@@ -315,7 +315,7 @@ collect(execution: ToolExecution): DshEnvironment
 list(): BashEnvVariableInfo[]
 ```
 
-Types: [DshEnvironment](../core-data-structures/bash.md) · [ToolExecution](../core-data-structures/tools.md)
+Types: [DshEnvironment](../core-data-structures/process.md) · [ToolExecution](../core-data-structures/tools.md)
 
 Source: [`packages/bash/tool-bash/src/index.ts:104`](../../packages/bash/tool-bash/src/index.ts)
 
@@ -829,6 +829,31 @@ Types: [Agent](../core-data-structures/core.md)
 
 Source: [`packages/plan/plan-mode/src/index.ts:141`](../../packages/plan/plan-mode/src/index.ts)
 
+## `ctx.processes` — `ProcessManager` (abstract seam)
+
+Abstract process manager. Subclass, implement spawn, and load the subclass as a plugin — it registers as `ctx.processes` (one implementation per context; loading a second throws, which is cordis' standard duplicate-service behavior).
+
+Implementations must honor these semantics:
+
+- spawn returns immediately with a live handle; `done` resolves at process close and rejects only for spawn-level failures.
+- Output readers are offset-based and non-consuming, so independent readers never consume one another's output; lossy reads report truncation and the spill file holding the complete stream when one exists.
+- ProcessHandle.kill and the spec's abort signal escalate SIGTERM→grace→SIGKILL across the whole process group.
+- Disposal kills all still-running managed processes and awaits their exit.
+
+```ts cordis-catalog
+/**
+ * Start one managed child process from a fully-specified spec; this seam
+ * applies no defaults.
+ * @param spec - argv, directory, limits, grace, cancellation, and environment.
+ * @returns the live process handle (readers, kill, outcome promise).
+ */
+abstract spawn(spec: ProcessSpawnSpec): ProcessHandle
+```
+
+Types: [ProcessHandle](../core-data-structures/process.md) · [ProcessSpawnSpec](../core-data-structures/process.md)
+
+Source: [`packages/process/process/src/index.ts:48`](../../packages/process/process/src/index.ts)
+
 ## `ctx.pty` — `PtyService`
 
 In-process registry for replaceable PTY backends and exact-Agent sessions.