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/sdk/helper/src/features/builtin/index.ts

@@ -32,7 +32,10 @@ export function createBuiltinRegistry(profile: ProjectProfile): FeatureRegistry
       summary: 'Command execution',
       mode: 'exclusive',
       required: true,
-      baseResources: [{ kind: 'npm-cordis-config-entry', id: 'tool-bash', package: '@deepseek-ai/dsh-tool-bash' }],
+      baseResources: [
+        { kind: 'npm-cordis-config-entry', id: 'processes', package: '@deepseek-ai/dsh-process-local' },
+        { kind: 'npm-cordis-config-entry', id: 'tool-bash', package: '@deepseek-ai/dsh-tool-bash' },
+      ],
       options: [
         {
           id: 'local',