fix(docs): address Codex review on the architecture rewrite

- session.md § TurnEndReasonMap now carries the full precedence rule
  the old architecture.md stated and the loop implements (loop.ts's
  stepFinishReason carry-forward): max-tokens wins over completed only;
  disposed/aborted/error take precedence. The architecture.md pointer
  was otherwise citing an incomplete home.
- The cookbook feature-map compaction row no longer reads as if a
  model-facing /compact tool ships: a manual trigger invokes the same
  ctx.compact routine; the consumer tool is deferred per the
  compaction RFC.

docs/core-data-structures/session.md

@@ -216,7 +216,7 @@ interface TurnEndReasonMap {
 }
 ```
 
-`max-tokens` mirrors the model-call `FinishReason` of the same name: any `max-tokens` step in a turn makes the whole turn end `max-tokens` (the cut-short fact wins over a later continuation), so a consumer can tell a clean stop from a truncated one. `rejected` is a zero-step turn whose whole prompt batch an `agent/prompt-submit` hook blocked (the ACP bridge maps it to `cancelled`). `interrupted` is the one reason no loop emits — it is synthesized by crash recovery (see [persistence.md](persistence.md)). Both maps are merge-extensible.
+`max-tokens` mirrors the model-call `FinishReason` of the same name: any `max-tokens` step in a turn makes the whole turn end `max-tokens` rather than `completed` (the cut-short fact wins over a later continuation), so a consumer can tell a clean stop from a truncated one — but only over `completed`: the `disposed`/`aborted`/`error` outcomes take precedence. `rejected` is a zero-step turn whose whole prompt batch an `agent/prompt-submit` hook blocked (the ACP bridge maps it to `cancelled`). `interrupted` is the one reason no loop emits — it is synthesized by crash recovery (see [persistence.md](persistence.md)). Both maps are merge-extensible.
 
 ## The turn-enclosure invariant