feat: add dry-run workflow execution boundary

services/orchestrator/README.md

@@ -72,9 +72,22 @@ window and never changes the runtime mode. The first gate requires:
 Passing the gate means only `manual_canary_review`; it does not authorize or
 activate Canary routing.
 
+Phase 3 adds the execution handoff boundary without enabling it:
+
+- `workflow-execution-request-v1` normalizes authorization, timeout,
+  cancellation, fallback, and idempotency controls;
+- `workflow-execution-decision-v1` separates the candidate engine from the
+  effective executor;
+- Canary and Active selections emit auditable `workflow_execution_planned`
+  events;
+- the effective engine remains Native and non-Native dispatch throws
+  `WORKFLOW_EXECUTION_HANDOFF_DISABLED`;
+- the implementation capability is hard-disabled in code, so memindadm
+  configuration cannot accidentally unlock execution.
+
 The default memindadm mode remains `off`. Canary and Active routing are not
-wired to the LangGraph executor in Phase 2. Native Agent Run remains the sole
-executor, including in Shadow mode.
+wired to the LangGraph executor in Phase 3. Native Agent Run remains the sole
+executor in every mode.
 
 ## Admin configuration
 
@@ -84,8 +97,10 @@ Supported modes:
 
 - `off`: Native Agent Run only.
 - `shadow`: Native executes; the configured engine may observe.
-- `canary`: user allowlist and deterministic rollout percentage.
-- `active`: the primary engine handles workflow-allowlisted tasks.
+- `canary`: user allowlist and deterministic rollout percentage produce
+  Dry-run candidate decisions.
+- `active`: workflow-allowlisted tasks produce Dry-run primary-engine
+  decisions.
 
 `MEMIND_ORCHESTRATOR_KILL_SWITCH=1` always forces Native selection.