fix(transactions): allow re-linking a bank tx stranded on a reversed verifikat (#988) (#1009)

* fix(transactions): allow re-linking a bank tx stranded on a reversed verifikat (#988)

A transaction whose journal_entry_id points at a reversed/cancelled entry reads
as "utan koppling" in the UI (the transactions page enriches only status='posted'
links), yet the re-booking guards treated ANY non-null pointer as "already
linked". So a storno'd/corrected transaction could never be linked to another
verifikat or re-categorized: the exact symptom in issue #988.

Add a shared hasLiveJournalEntryLink() predicate used by every re-booking guard
(linkTransactionToJournalEntry, manualLink, categorize-core, and the MCP link
stage-check): a pointer at a non-posted entry is treated as re-linkable, and the
two optimistic-locked writes now lock on the exact previous pointer (null OR the
stale id) instead of always .is(null), so the overwrite goes through race-safely.
hasLiveJournalEntryLink fails closed on a read error so a transient blip can't
detach a genuinely live link.

The source was fixed in #726 (reverseEntry/correctEntry now detach/re-point the
tx); this makes the guards self-heal for the pre-#726 backlog and any future
best-effort miss.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

* fix(transactions): detect 0-row CAS before invoice effects; fix categorize commit test

Addresses PR review (CodeRabbit Critical + CI):

- link-journal-entry.ts: the tx UPDATE now .select('id') and treats a 0-row
  result as LINK_TX_TX_ALREADY_LINKED, failing BEFORE any invoice settlement /
  invoice_payments insert. Without this, a concurrent re-link that lost the CAS
  would still mark the invoice paid against a transaction we didn't link (same
  optimistic-lock contract manualLink already enforces).

- pending-operations commit route test: the categorize_transaction "already
  categorized" case now enqueues the hasLiveJournalEntryLink status read (posted
  = live) so it still returns 409. This was the core-only CI failure: the new
  liveness read in categorize-core consumed a queued response.

- Updated the link happy-path / invoice-race test enqueues to return a row for
  the now-selecting tx UPDATE.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

---------

Co-authored-by: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

lib/reconciliation/__tests__/bank-reconciliation.test.ts

@@ -709,12 +709,13 @@ describe('manualLink', () => {
     expect(result.error).toBe('Transaktionen kunde inte hittas.')
   })
 
-  it('rejects when transaction is already linked', async () => {
+  it('rejects when transaction is already linked to a LIVE (posted) entry', async () => {
     const { supabase, enqueue } = createQueueMockSupabase()
     const tx = makeTransaction({ id: 'tx-1', journal_entry_id: 'je-existing' })
 
-    // Transaction found but already linked
+    // Transaction found, still pointing at a live posted verifikat
     enqueue({ data: tx })
+    enqueue({ data: { status: 'posted' } }) // hasLiveJournalEntryLink: prior link is live
 
     const result = await manualLink(supabase as never, 'company-1', 'tx-1', 'je-1', 'user-1')
 
@@ -722,6 +723,24 @@ describe('manualLink', () => {
     expect(result.error).toBe('Transaktionen är redan kopplad till en verifikation.')
   })
 
+  it('re-links a transaction stranded on a reversed entry (#988)', async () => {
+    const { supabase, enqueue } = createQueueMockSupabase()
+    // Still carries a pointer at a status='reversed' entry (storno/correction
+    // left it behind). The UI shows it as "utan koppling", so manualLink must
+    // treat it as free and overwrite the stale pointer.
+    const tx = makeTransaction({ id: 'tx-1', journal_entry_id: 'je-reversed' })
+
+    enqueue({ data: tx }) // tx fetch
+    enqueue({ data: { status: 'reversed' } }) // hasLiveJournalEntryLink: stale link
+    enqueue({ data: { id: 'je-1', user_id: 'company-1', status: 'posted' } }) // target JE fetch
+    enqueue({ data: [{ debit_amount: 1000, credit_amount: 0, account_number: '1930' }] }) // line on 1930
+    enqueue({ data: [{ id: 'tx-1' }] }) // UPDATE .eq(stale id) → 1 row overwritten
+
+    const result = await manualLink(supabase as never, 'company-1', 'tx-1', 'je-1', 'user-1', '1930')
+
+    expect(result.success).toBe(true)
+  })
+
   it('rejects when journal entry has no line on the selected account', async () => {
     const { supabase, enqueue } = createQueueMockSupabase()
     const tx = makeTransaction({ id: 'tx-1', journal_entry_id: null })