docs(steering): N24 decided: gang-groups demoted to backlog as a co-start group

LLM training is one parallel job with topology requirements (PR-10).
gang-groups moves from the spec list to the roadmap backlog, re-scoped as
a co-start group of separately managed jobs and services (RL
post-training, disaggregated serving, streaming pipelines). resource-model
phases and the brief updated; job-resize no longer resizes gang groups.

Co-Authored-By: Claude Opus 5.5 (1M context) <noreply@anthropic.com>

.kiro/steering/resource-model.md

@@ -113,8 +113,7 @@ rules of the resource-provisioner contract
   resize or replica replacement. Examples: checkpoint volumes (one writer
   gang), model weights (read-many by every replica), dataset caches.
 - **States:** `PENDING → PREPARING → READY → RELEASING → RELEASED/FAILED`.
-  Dispatch waits until every claim of the job (or of the whole gang) is
-  READY.
+  Dispatch waits until every claim of the job is READY.
 
 ## Rules every resource design must keep
 
@@ -173,10 +172,12 @@ device-plugin **wire protocols** is open decision 4.
   `same[]`/`span[]` already pack against.
 - **MIG/MPS:** partitions are reported as instances. Changing a layout is a
   provider action that drains the GPU, never a scheduler decision.
-- **Gangs:** one parallel job is already placed all-or-nothing
-  (`parjob-placement`). A gang of several jobs (launcher plus workers) needs
-  a gang group; the whole gang and its claims are READY before any part
-  starts.
+- **Gangs:** training is **one parallel job** (decided 2026-10-12, N24 in
+  `resource-questions.md`). One parallel job is already placed
+  all-or-nothing (`parjob-placement`), and compound resreqs mix roles
+  inside it. A gang of several jobs (`gang-groups`, backlog) is only for
+  roles that need separate lifecycles, profiles or owners: RL
+  post-training, disaggregated serving, streaming pipelines.
 - **Elastic resize and restart:** standalone claims are re-bound to the new
   host set.
 - **Serving:** replicas share one read-many weights claim and have
@@ -198,8 +199,12 @@ device-plugin **wire protocols** is open decision 4.
    the provider contract, worker prepare/publish, and a stage-in/stage-out
    gate. First users: sandbox scratch, `transfer_files` staging,
    checkpoint volumes.
-5. **`gang-groups`:** gangs of several jobs. Claim re-attach in `job-resize`
-   and shared weights claims in `service-replica-set` rollouts.
+5. **Claim users in existing specs:** claim re-attach in `job-resize`, and
+   shared weights claims in `service-replica-set` rollouts.
+
+`gang-groups` is not a phase. It is in the roadmap backlog as a co-start
+group for RL post-training, disaggregated serving and streaming pipelines
+(N24).
 
 **Config-only now:** document the static custom resources that already
 work.