docs, hive-c0re: retire prose describing the removed get_loose_ends target

Follow-up to 729c5b4f42, which dropped the
`agent` parameter from get_loose_ends and deleted Capability::QueryAgentState
with it. Three prose sites still describe the interface that commit removed:

- socket_server/mod.rs's module doc claimed authority on this socket derives
  from "capabilities for the hive-wide queries and tool-group membership for
  the orchestration verbs". There are no capability-gated queries left —
  `git grep -n has_cap -- hive-c0re/src/socket_server/` returns nothing, and
  require_group("scheduling") is the only gate in dispatch_orchestration.
- agent-hierarchy.md listed loose-ends visibility ("manager sees hive-wide,
  sub-agents only their own") as one of the manager-only overrides that
  "exist across hive-c0re today". It doesn't, and the sentence pointed a
  reader at loose_ends.rs for owner-check logic that is no longer there.
- conventions.md's Loose-ends wire shape still spoke of "the agent-flavour
  and manager-flavour requests" and "the agent-flavour list". There is one
  request shape.

No behaviour change: prose only.

Refs #4480

docs/agent-lifecycle/agent-hierarchy.md

@@ -132,15 +132,17 @@ Manager}` switch picks the MCP tool allow-list claude sees. Both are
   container including the manager, so all token/state paths resolve
   through it the same way everywhere.
 - **Scattered ownership checks** — a handful of independent
-manager-only overrides exist across `hive-c0re` today: loose-ends
-visibility (manager sees hive-wide, sub-agents only their own),
-`destroy` refusing to act on the manager, and crash-watch skipping
+manager-only overrides exist across `hive-c0re` today: `destroy`
+refusing to act on the manager, and crash-watch skipping
 the manager (it autorestarts via systemd instead of going through
 the crash-watch loop). Each is planned to become a capability
 check instead of a manager-name check — see the
-module docs for `loose_ends.rs`, `stores/broker.rs`, `actions.rs`,
+module docs for `stores/broker.rs`, `actions.rs`,
 and `workers/crash_watch.rs` for the current owner-check logic in
-each. (The harness handles reminder cancellation fully in-agent — see
+each. Loose-ends visibility used to be on this list; it isn't a
+manager override any more — `GetLooseEnds` takes no target and every
+agent, `ruth` included, sees only its own rows.
+(The harness handles reminder cancellation fully in-agent — see
 the note on `CancelLooseEndKind::Reminder` in
 `hive-c0re/src/socket_server/mod.rs`.)
 <!-- vale write-good.Passive = YES -->