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/process/conventions.md

@@ -165,8 +165,8 @@ the dashboard's "mark all read" (unbounded, per-agent).
 
 ### Loose-ends wire shape
 
-`LooseEnd` is the per-row response shape for `GetLooseEnds` (both
-the agent-flavour and manager-flavour requests). Tagged enum so
+`LooseEnd` is the per-row response shape for `GetLooseEnds` — one
+request shape, no per-socket flavours. Tagged enum so
 new thread kinds (forge PRs, long-running approvals from a
 privileged bot, etc.) can land later without breaking existing
 handlers. Each row carries enough context that the caller renders
@@ -194,7 +194,7 @@ Per-variant fields:
 - `PendingMessages { count }` — undelivered inbox messages the
   agent still owes itself a `recv` for. Informational + not
   cancellable (drain with `recv`); only emitted when `count > 0`,
-  and surfaced first in the agent-flavour list as the most
+  and surfaced first in the list as the most
   actionable signal. Counted host-side from the broker
   (`count_pending`), so it reflects what's genuinely still queued —
   the wake-message that drove the current turn is already delivered