docs: fix argus R4 review nits on config-PR merge docs

- hive-c0re/README.md: drop deleted webhook_secret.rs from the module
  list
- docs/swarm/README.md, docs/agent-lifecycle/approvals.md: rewrite
  temporal wording (legacy/older-release phrasing) as current
  behaviour
- docs/swarm/README.md: note that a lost closed delivery deploys
  nothing and how the operator recovers

docs/agent-lifecycle/approvals.md

@@ -1,8 +1,8 @@
 # Approvals + helper events
 
 The approval queue is where an agent asks the operator for something it
-can't do itself: a scheduled prompt, or (legacy rows only) a meta-input
-bump. Config changes don't go through this queue: they're pull requests
+can't do itself: a scheduled prompt, or a meta-input bump. Config
+changes don't go through this queue: they're pull requests
 on the agent's config repo, which an operator merges on the forge, and
 that merge deploys them. The submitting agent — any agent with the
 `approvals` tool group, which manages the config of its **direct
@@ -23,10 +23,9 @@ it stays informed about what happens after a decision lands.
   directly from the SCH3DUL3S tab, which skips this approval step
   entirely — the gate here is specifically for an *agent* asking to
   schedule something, not for you doing it.
-- **Meta/flake update** (`UpdateMetaInputs`) — legacy: nothing queues
-  this kind, but an existing row still reads back and you can approve it.
-  Approving runs the update and commits the lock change; it doesn't
-  rebuild anything by itself.
+- **Meta/flake update** (`UpdateMetaInputs`) — an existing row reads
+  back and you can approve it. Approving runs the update and commits
+  the lock change; it doesn't rebuild anything by itself.
 
 Don't want to approve something? **Deny it** (`DENY` on the dashboard
 card, or `hivectl approvals deny <id>`) — nothing runs. Either way the