feat(parties): phase 1 substrate, one party per counterpart (#2162)

* feat(parties): phase 1 substrate, one party per counterpart

Adds the identity layer above customers and suppliers, which keep their
tables and every foreign key and gain a nullable party_id.

- parties: company-scoped identity with status (suggested | confirmed),
  kind, alias keys, origin and merged_into. One live party per org number
  and company, enforced by a partial unique index; merged losers leave the
  index so a merge can be undone. This is the unique key the
  duplicate-invoice guard has lacked, since suppliers never had one.
- party_facts: statements with a source, a rank (preferred | normal |
  deprecated) and two time axes, never overwritten.
- party_identities: bankgiro, plusgiro, IBAN and friends per party, with
  seen and paid counts and a known | unverified status.
- party_decisions: every human action on a party as a labelled example.
- normalize_org_number(text): SQL mirror of lib/invariants/org-number.ts
  (strip separators, drop the century on 12 digits, Luhn check, 10 digits).
- ensure_party(): find by org number inside the company, else create.
  Name-only rows never merge at insert time; a name merge is a recorded
  human decision.
- Backfill: one party per existing supplier and customer, merged on org
  number, suppliers first so both roles land on one party.
- Archive contract: the four tables are master data in the full archive.

Observed parties (keys derived from voucher and bank text) are not stored;
they stay computed by the ledger-context RPC. No posted entry is touched.

Co-Authored-By: Claude Fable 5.1 <noreply@anthropic.com>

* fix(parties): tenant-safe composite foreign keys on every party link

Facts, identities, decisions, customers.party_id, suppliers.party_id and
parties.merged_into now reference parties(id, company_id), so a row can
only point at a party in its own company. ON DELETE SET NULL names
party_id so role rows keep their company_id. Adds a pg-real test that
rejects every cross-company link and checks company_id survives a party
delete.

Co-Authored-By: Claude Fable 5.1 <noreply@anthropic.com>

---------

Co-authored-by: Jakob Wennberg <311770904+jakobwennberg-oss@users.noreply.github.com>
Co-authored-by: Claude Fable 5.1 <noreply@anthropic.com>

DECISIONS.md

@@ -1494,7 +1494,9 @@ One line per decision: `[YYYY-MM-DD] <decision>: <why>`. Appended by agents and
 [2026-09-02] BankID signup no longer returns a magic link: the account is created unconfirmed and the typed address must click a mailed link before bankid_linked (and the MFA exemption) is set. Chosen over a pending-signup table: one nullable column (bankid_identities.email_verified_at) and the existing auth callback carry the state.
 [2026-09-02] Removed the skattekonto drift email (skattekonto.drift_detected event, handler, /api/extensions/skatteverket/skattekonto/drift route, cron hook) instead of fixing it: it alerted on raw saldo-vs-1630 gaps that unbooked rows explain by construction (2026-09-02: Arcim 35 842 kr, 100% explained, while the Hem notice and reconciliation page said nothing was wrong), repeated every 24 h, and was the only surface of a May-2026 feature whose promised dashboard tile was never built. Since 2026-08-25 the reconciliation page and the Hem notice (detectSkvUnexplained, gated on unexplained_difference) are the surface. Considered gating the mail on unexplained_difference + once per episode (built, then dropped): after that gate it only fires on integrity findings the engine itself calls 'never a user task'. skattekonto_drift_tolerance stays (Hem notice reads it); stale skattekonto_drift_last_alert_at rows in extension_data are inert.
 [2026-09-02] parties phase 0, golden set stays out of git: the labelling sample is prod voucher text with person names (salary, expense claims) and the repo is public, so the draw SQL is versioned but the rows and labels live in gitignored dev_docs/parties/golden/.
+[2026-09-02] parties substrate: customers and suppliers keep their tables and gain party_id; parties dedupe on normalised org number only, never on name at insert time. A name merge is a recorded human decision because the July measurement showed a majority of generic keys still map to one real vendor, so an automatic name merge would fuse unrelated suppliers.
 [2026-09-02] MCP eager-auth flag (`auth=required`) on the claude.ai connector links instead of reverting lazy auth: claude.ai's two-step Add-custom-connector dialog probes the URL without credentials and pre-fills Authentication "None" when the lazy handshake answers 200, which blocks the sign-in later; per Anthropic's docs a 401 is the only answer it reads as OAuth. The flag lives in the URL, so the links we control (Settings, onboarding checklist, both docs pages, website) get OAuth detected while the bare URL keeps lazy auth for Claude Code, the plugin, Cursor and ChatGPT, and existing connector records stay untouched. Rejected: keying eager auth off `client=claude-connector` (documented as telemetry-only) and sniffing the probe's user agent (fragile, undocumented).
 [2026-09-02] Agent-triggerable bank sync shipped (v1 POST /bank-connections/{id}/sync + MCP gnubok_sync_bank), lifting the 2026-09-01 deferral: Emil chose to close every open F2 item in one PR. The cost worry is bounded structurally instead of by policy: the window is never caller-controlled (gap-aware 7 to 90 days, same helper as the cron), a connection synced within 15 minutes answers BANK_SYNC_COOLDOWN with next_allowed_at (MCP returns it in-band as synced=false so agents read on instead of retrying), and failures are throttled per process by attempt time. The web Synka-nu route is left untouched rather than refactored onto the shared runner: it carries UI-only behaviour (caller-chosen days_back up to 365, SIE sweep stamping) and a regression there would hit every user for a code-sharing win.
 [2026-09-02] Bank-sync cooldown is a durable lease column (bank_connections.sync_lease_until, migration 20260902150000) claimed with one conditional UPDATE, not a process-local attempt map: the security scan on PR #2165 showed the map is bypassed by a second serverless instance or a cold start, so two agent calls could each bill Enable Banking. A column add was chosen over reusing extension_data because PostgREST cannot express an atomic conditional upsert there; the nightly cron deliberately ignores the lease.
 [2026-09-02] Grok links carry auth=required like the claude.ai link (#2159), decided from a live test: on the lazy URL Grok's connector dialog listed all 150+ tools and never opened the sign-in, so it reads the 200 probe as an authless server exactly as claude.ai does. The flag lives in one helper (mcpServerUrl / sideDoorServerUrl in lib/onboarding/checklist.ts) so the settings row, the onboarding side door and the deep link cannot drift; ChatGPT stays lazy because its developer mode honours the 401 on the first protected call.
+[2026-09-02] parties children/roles reference parties(id, company_id) with composite FKs, not parties(id): a party UUID from another tenant is rejected by construction instead of relying on each writer to check; ON DELETE SET NULL (party_id) on customers/suppliers because a plain SET NULL would null company_id too (Superagent P2 on #2162)