fix(psa): resource assignment targets CW owner, status PATCH verifies apply

Previous `resources`-string PATCH was silently ignored by CW — the
`resources` field is server-derived from the ticket's owner + schedule
entries, not freely writable. Status PATCH could also silently no-op
when a cross-board status id was sent.

- add_resource: when the ticket is unassigned, set the `owner`
  MemberReference (the canonical writable primary-assignee field).
  If already owned by someone else, append the identifier to the
  `resources` co-assignee string best-effort.
- remove_resource: clear `owner` (with remove→replace:null fallback) if
  the target is the current owner, otherwise strip from `resources`.
- list_resources: merge owner + resources string, deduped by member id,
  so the UI reflects both single-owner and multi-resource assignments.
- update_ticket_status: verify CW applied the status by comparing the
  response body's status.id — raises PSAError with a clear message when
  CW silently rejects the change (e.g., status invalid for ticket's
  board), instead of reporting spurious success.
- Frontend: surface the backend error detail in the toast so users see
  the real reason instead of a generic "Failed to update" message.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

frontend/src/components/tickets/detail/TicketDetailHeader.tsx

@@ -1,4 +1,5 @@
 import { useState } from 'react'
+import axios from 'axios'
 import { ticketsApi } from '@/api/tickets'
 import { toast } from '@/lib/toast'
 import type { PSATicketSearchResult, PSATicketStatusItem } from '@/types/integrations'
@@ -22,8 +23,11 @@ export function TicketDetailHeader({ ticket, currentStatusId, currentStatusName,
       const result: PSATicketStatusUpdate = await ticketsApi.updateStatus(Number(ticket.id), statusId)
       onStatusUpdated(result.ticket_id, result.new_status, result.new_status_id)
       toast.success(`Status updated to ${result.new_status}`)
-    } catch {
-      toast.error('Failed to update status')
+    } catch (err) {
+      const detail = axios.isAxiosError(err)
+        ? (err.response?.data as { detail?: string })?.detail
+        : undefined
+      toast.error(detail || 'Failed to update status')
     } finally {
       setUpdating(false)
     }

frontend/src/components/tickets/detail/TicketResourceManager.tsx

@@ -1,4 +1,5 @@
 import { useState } from 'react'
+import axios from 'axios'
 import { UserPlus, X, User } from 'lucide-react'
 import { ticketsApi } from '@/api/tickets'
 import { toast } from '@/lib/toast'
@@ -27,8 +28,11 @@ export function TicketResourceManager({ ticketId, resources, allMembers, onChang
       setAdding(false)
       setSelectedMemberId('')
       onChanged()
-    } catch {
-      toast.error('Failed to add resource')
+    } catch (err) {
+      const detail = axios.isAxiosError(err)
+        ? (err.response?.data as { detail?: string })?.detail
+        : undefined
+      toast.error(detail || 'Failed to add resource')
     } finally {
       setBusy(null)
     }
@@ -40,8 +44,11 @@ export function TicketResourceManager({ ticketId, resources, allMembers, onChang
       await ticketsApi.removeResource(ticketId, memberId)
       toast.success('Resource removed')
       onChanged()
-    } catch {
-      toast.error('Failed to remove resource')
+    } catch (err) {
+      const detail = axios.isAxiosError(err)
+        ? (err.response?.data as { detail?: string })?.detail
+        : undefined
+      toast.error(detail || 'Failed to remove resource')
     } finally {
       setBusy(null)
     }