FN-9112: default Memory Keeper heartbeats to disabled

Default built-in Memory Keeper agents to opt-in heartbeat scheduling while retaining operator choices.

- Provision new Memory Keeper agents with heartbeat disabled and hourly scheduling preconfigured.
- Preserve explicit heartbeat settings during startup convergence and avoid no-op rewrites.
- Add provisioning coverage, operator documentation, and a release changeset.

Files changed:
 .../fn-9112-memory-keeper-heartbeat-default-off.md |  7 +++
 docs/agents.md                                     |  2 +-
 .../__tests__/memory-agent-provisioning.test.ts    | 59 +++++++++++++++++++---
 packages/core/src/agents/agent-store.ts            | 34 ++++++++++---
 4 files changed, 86 insertions(+), 16 deletions(-)

Fusion-Task-Id: FN-9112

Fusion-Task-Lineage: 49edc6d9-3d9b-412f-91a5-c26f4a26a662

Co-authored-by: Fusion (runfusion.ai) <noreply@runfusion.ai>

docs/agents.md

@@ -1738,7 +1738,7 @@ Per-agent overrides via `runtimeConfig`:
 
 ## Memory Keeper (FN-8932)
 
-Each project provisions a durable **Memory Keeper** custom agent for deterministic, hourly memory upkeep. It is heartbeat-enabled and has task auto-claim disabled, so it cannot claim board work or make product decisions. Provisioning identifies the owner by its provenance marker, not its display name: if an operator already owns `Memory Keeper`, Fusion creates `Memory Keeper (built-in)` instead; if both names are occupied, startup continues without a memory agent rather than renaming/adopting the operator agent or failing initialization.
+Each project provisions a durable **Memory Keeper** custom agent for deterministic memory upkeep. It is heartbeat-disabled by default, so consolidation is opt-in: enable its heartbeat from Agent Detail when you want the hourly schedule to run. Task auto-claim remains disabled, and the one-hour heartbeat interval is preconfigured for that later opt-in, so it cannot claim board work or make product decisions. Provisioning identifies the owner by its provenance marker, not its display name: if an operator already owns `Memory Keeper`, Fusion creates `Memory Keeper (built-in)` instead; if both names are occupied, startup continues without a memory agent rather than renaming/adopting the operator agent or failing initialization. Later startups preserve an operator's explicit heartbeat choice in either direction.
 
 When enabled, a heartbeat refreshes the knowledge graph incrementally, appends deterministic FNXC rationale decisions through recall deduplication, then merges rationale/file node identifiers into each resulting recall record. Cross-references only grow: the per-record PostgreSQL advisory lock reads, unions, and writes in one transaction, and equal unions perform no update. Pruning is intentionally out of scope. A fingerprint-stable graph, duplicate recall results, and equal cross-reference unions yield a no-write tick; an in-process `(agentId, projectId)` guard skips re-entry. The guard is defense-in-depth for manual callers and does not fence another process or CLI graph build.