refactor(tasks): split the task registry into seam and local implementation

The tasks/ family now matches the capability-seam shape: @deepseek-ai/dsh-tasks
keeps the abstract TaskService (ctx.tasks contract, vocabulary types, snapshot
invariant companion) and the new @deepseek-ai/dsh-tasks-local carries the
process-local registry (LocalTaskService: in-memory store, settlement,
owner-cleanup effects, teardown, TASK_WAIT_TIMEOUT). Compositions and test
harnesses now load dsh-tasks-local; producers, TaskKindMap merges, and
dsh-tool-tasks keep importing the seam only.

Producer misconfiguration diagnostics name dsh-tasks-local because loading the
implementation is the fix. The registry behavior suite moves to tasks-local;
the seam keeps a stub-subclass registration test and the probe-based invariant
suite.

packages/examples/agent-spine-demo/src/index.ts

@@ -22,7 +22,7 @@ import AgentRegistry from '@deepseek-ai/dsh-agent'
 import GoalService, { type Config as GoalDomainConfig } from '@deepseek-ai/dsh-goal'
 import * as goalSession from '@deepseek-ai/dsh-goal-session'
 import * as toolGoal from '@deepseek-ai/dsh-tool-goal'
-import TaskService from '@deepseek-ai/dsh-tasks'
+import LocalTaskService from '@deepseek-ai/dsh-tasks-local'
 import InvariantService, { type Config as InvariantConfig } from '@deepseek-ai/dsh-invariants'
 import * as sessionInvariant from '@deepseek-ai/dsh-session/invariant'
 import * as agentInvariant from '@deepseek-ai/dsh-agent/invariant'
@@ -223,7 +223,7 @@ export function apply(ctx: Context, config: Config): void {
     ctx.plugin(toolGoal, config.goals.tool ?? {})
     ctx.plugin(goalSession)
   }
-  ctx.plugin(TaskService)
+  ctx.plugin(LocalTaskService)
   ctx.plugin(InvariantService, config.invariants ?? {})
   ctx.plugin(sessionInvariant)
   ctx.plugin(agentInvariant)