#5002: the orphan recovery goes both ways

#4806 gave a site admin one write on a help desk group nobody is left to
run, and #4926 made the Person field of that form a people search. Neither
closed the other half: `storeAgent()` was gated on
requireManagerAccessOrOrphanRecovery(), `destroyAgent()` on plain
requireManagerAccess(). So the rescue could appoint and never un-appoint —
the row it had just written sat in the rescuer's own Agents list marked
"Not yours to manage", with no Remove control and a 403 behind the DELETE.

A `manager` press was worse: the write ends the orphan state, so the group
left `orphanedGroupIds` and the admin could not remove the row, appoint
anybody else, or appoint themselves. The only person who could undo it was
the person wrongly appointed — #4806's frozen group, reached through
#4806's cure.

destroyAgent() now asks requireRemoveAccess(): a manager of the group, or a
site admin while the group is STILL orphaned (symmetric with the write and
strictly narrower — on such a group they could appoint themselves and then
remove anything anyway), or a site admin undoing a row their own rescue
wrote. That last arm needs provenance, hence `recovered_by`: "the group
would be orphaned without this row" cannot tell a mistaken appointment from
the sole working manager of a healthy group, and admitting the second would
let any admin strip a manager and seize the desk (#4710). The stamp is
cleared the moment a manager of the group writes the row themselves.

`removableAgentIds` is that gate in prop form, so the Remove button and the
DELETE cannot disagree, and the confirmation says when a removal hands the
group back to having nobody.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>

src/Models/TicketingAgentAccess.php

@@ -9,7 +9,13 @@ class TicketingAgentAccess extends Model
 {
     protected $table = 'ticketing_agent_access';
 
-    protected $fillable = ['user_id', 'group_id', 'role'];
+    /**
+     * `recovered_by` is #5002: the site admin who wrote this row as an orphan
+     * recovery (#4806), and may therefore take it back. Null on every row
+     * written by an ordinary manager — see the migration for why this is not
+     * a general-purpose `created_by`.
+     */
+    protected $fillable = ['user_id', 'group_id', 'role', 'recovered_by'];
 
     public function group(): BelongsTo
     {