docs: qualify plan-mode timing and workspace no-write claims

ds-review-bot round 3:
- set() after a turn's final step lands in a later turn (selection
  never forces continuation) — the same-turn phrasing overstated the
  guarantee; set() JSDoc + subsystem page (both languages).
- Workspace attach/insert/detach no-op claims now carry the
  filtered-candidate-prune caveat: mutate() durably prunes stale
  candidates even when the requested change is a no-op, a state the
  sessionIds contract explicitly permits; Workspace fence re-synced on
  both page sides; catalogs regenerated.

docs/subsystems/core.i18n.yaml

@@ -2,5 +2,5 @@
 # side as of the last confirmed-consistent state. Both languages carry equal authority;
 # after editing either side, bring the other along and re-record with:
 #   pnpm run verify-translation-pairing --write docs/subsystems/core.md
-core.md: 1d0bf6c61500817860dfdd452bddc25adbbeffcc
-core.zh.md: 2b4766dcfcf1901de2bb8a8f9168888a67af7fba
+core.md: 3a8ccbef4163eabba1cd287284eda68135f2db13
+core.zh.md: 0cd6a57971ee98c75b52dd45b6f648632dab8a90