feat(tasks): background task runtime, generic task_* control tools, bash/subagent producers

One shared ctx.tasks registry (branded <kind>-N ids, owner-fenced
read/kill/wait/list, attachSurface misconfiguration fence, reported-flag
notice dedup, atomic register) + dsh-tool-tasks (task_output/task_list/
task_kill, completion-notice injection, background prompt habit).
Producers opt in via their own enableRunInBackground config: bash
(stream kind; seam slimmed to resolve/run/start returning a BashProcess
handle, bash_output/bash_kill deleted) and subagent (final-output kind;
done settles after run.dispose()). Owner disposal drains tasks through
the new awaited ctx.agents.onCleanup seam in the loop's disposal chain.
Both RFCs moved to implemented/; docs, catalogs, snapshots re-pinned.

packages/ui/acp-agent/tests/acp-agent.spec.ts

@@ -70,7 +70,9 @@ describe('dsh-acp-agent composition', () => {
       })
     }
     const assembly = await ctx.get('systemPrompt')!.assemble()
-    expect(assembly.tools.map(tool => tool.name)).toEqual(['zulu', 'alpha'])
+    // The rest-slot is lexicographic: the bundle's own task control tools
+    // (tool-tasks needs no executor, unlike the pending bash tool) follow alpha.
+    expect(assembly.tools.map(tool => tool.name)).toEqual(['zulu', 'alpha', 'task_kill', 'task_list', 'task_output'])
     await ctx.fiber.dispose()
   })
 

packages/ui/acp/README.md

@@ -35,7 +35,7 @@ The `initialize` handshake reports a fixed server identity (`agentInfo: { name:
 
 The bridge multiplexes N sessions over one connection. Live sessions are held in a `Map<sessionId, SessionRecord>` (forward) with a `WeakMap<Agent, sessionId>` reverse map so `agent/*` events — which carry only the `Agent` — demux in O(1). Every `session/event` and `agent/status` is routed strictly to its owning record, so concurrent sessions never cross-settle or interleave their `session/update` notifications. State is per session: one in-flight prompt each, `session/cancel` aborts and settles only its own agent/prompt, and disposal drains every live session in parallel to quiescence. (Per-session *permission* ownership is reserved for the deferred permission gate — `TODO(rfc010-permission-gate)`.)
 
-Background-task isolation rides on `dsh-tool-bash`: bash task ids are global and predictable, so each task carries an opaque owner token — the owning agent's `session.header.id` — stored on the task inside the executor (`dsh-bash`'s `ownerOf(id)` seam). `bash_output`/`bash_kill` reject a task whose token differs from the caller's session token, so one session's agent can't read or kill another's task. Ownership is by session TOKEN, not `Agent` object identity — a different `Agent` object on the same session may access the task — and because the token lives on the executor's task it survives a `tool-bash` HMR reload.
+Background-task isolation rides on the `ctx.tasks` runtime (`dsh-tasks`): task ids are global and predictable, so every read/kill/wait/list is fenced to the owning agent's session (`session.header.id`), and one session's agent can't read or kill another's task through `task_output`/`task_kill`. Ownership is by session token, not `Agent` object identity — a different `Agent` object on the same session may access the task — and because the registration lives in the tasks service it survives a producer-plugin HMR reload.
 
 ## Per-session cwd
 

packages/ui/stdio-agent/tests/stdio-agent.spec.ts

@@ -92,7 +92,9 @@ describe('dsh-stdio-agent app', () => {
       })
     }
     const assembly = await ctx.get('systemPrompt')!.assemble()
-    expect(assembly.tools.map(tool => tool.name)).toEqual(['zulu', 'alpha'])
+    // The rest-slot is lexicographic: the bundle's own task control tools
+    // (tool-tasks needs no executor, unlike the pending bash tool) follow alpha.
+    expect(assembly.tools.map(tool => tool.name)).toEqual(['zulu', 'alpha', 'task_kill', 'task_list', 'task_output'])
     await ctx.fiber.dispose()
   })