docs: consolidate agent execution and custody

docs/adr/ADR-005-scheduled-agent-execution.md

@@ -37,14 +37,36 @@ end-to-end flow:
 ```
 activity-core cron
   → context resolver (roster ∩ repos with schedule.yml)
-  → task per (repo, agent)
-  → coding-agent session runs `kaizen-agentic schedule prepare <agent>`
+  → durable work per (repo, agent)
+  → governed runner executes `kaizen-agentic schedule prepare <agent>`
   → session executes the agent instructions in that repo
 ```
 
 kaizen-agentic's responsibilities are exactly two: **declare** the schedule
 (`.kaizen/schedule.yml`) and **prepare** an orientation bundle for a run. It
-does **not** fire cron, create tasks, or invoke Claude.
+does **not** fire cron, own the durable work queue, or invoke an LLM.
+
+### Current runtime realization (2026-08-20)
+
+The initial contract above remains valid, but the generic word “task” now has a
+specific durable implementation:
+
+```
+activity-core Temporal schedule/event
+  → rule evaluation and eligibility
+  → unique, idempotent ops_run with lease/retry state
+  → rein-aharness claim loop
+  → agent-session approach and governed runtime/profile resolution
+  → kaizen-agentic schedule prepare <agent>
+  → bounded coding-agent session
+  → ops_run result + State Hub progress + .kaizen metrics/artifact evidence
+```
+
+`activity-core` owns schedule and durable work state. `rein-aharness` owns
+claiming, execution policy, credential routing, runtime selection, and bounded
+session operation. Kaizen Agentic continues to own declaration, agent craft,
+preparation, and improvement evidence. A human-started coding-agent session
+remains a supported execution mode and reference smoke path.
 
 ### 1. Schedule manifest — `.kaizen/schedule.yml`
 
@@ -123,10 +145,13 @@ kaizen-agentic schedule prepare <agent> [--target PATH] [--format markdown|json]
 
 ## Boundaries
 
-- **No scheduling code** in kaizen-agentic. Cron and task creation belong to
-  activity-core; the roster query belongs to state-hub.
+- **No scheduling or durable-queue code** in kaizen-agentic. Temporal schedules,
+  rule evaluation, and `ops_run` state belong to activity-core; the roster query
+  belongs to State Hub.
 - **No LLM invocation.** `prepare` produces a runner-agnostic bundle; a human or
-  automated coding-agent session executes it.
+  rein-aharness-governed coding-agent session executes it.
+- **No runtime authority or credentials.** Those remain with rein-aharness and
+  the ecosystem credential/authorization owners.
 - **State-hub schema changes** (roster opt-in flag) are designed here but
   implemented in `the-custodian` (repo boundary).
 
@@ -134,7 +159,7 @@ kaizen-agentic schedule prepare <agent> [--target PATH] [--format markdown|json]
 
 - Operators declare per-repo schedules and a fleet roster without tribal
   knowledge.
-- activity-core can fire recurring tasks referencing `schedule prepare`.
+- activity-core can fire recurring durable work referencing `schedule prepare`.
 - A scheduled session opens with full orientation (prompt + memory + metrics).
 - The existing `weekly-metrics-optimize` definition (ADR-004 / WP-0004) remains
   complementary; an `optimization` agent run may chain `schedule prepare