feat(transactions): AI booking proposal in the quick-review dialog (cascade step 3) (#1782)

Wires the auto-booking cascade to the UI. When the quick-review dialog opens
for a transaction, AiCategorizeProposal fetches POST /api/agent/categorize
(Tier 1 deterministic candidates → Tier 2 model selector, provider-agnostic)
and:

- pre-fills the dialog's account + VAT from the model's pick (through
  handleAccountChange, so class-2 VAT clearing is preserved),
- shows a confidence band (säker / trolig / välj konto), a short "Varför", and
  the candidate alternatives (click one to re-apply),
- falls back SILENTLY to the deterministic defaults on error, and shows a soft
  note when no AI backend is configured — the dialog always works without AI.

Surfaced inside the existing dialog (not a new card) so it reuses the proven,
balanced commit path. No silent auto-posting: "säker" is pre-filled and booked
with the dialog's existing one-tap Bokför; hands-off auto-book waits for
calibration (avoids any storno-on-undo).

lint + guards clean; 94 transaction/categorize tests green (no regressions).
Strings inline Swedish for now (lift to messages/{sv,en} pre-merge). UI PR:
awaiting founder visual sign-off before merge.

Co-authored-by: Jakob Wennberg <311770904+jakobwennberg-oss@users.noreply.github.com>
Co-authored-by: Claude Opus 4.8 <noreply@anthropic.com>

DECISIONS.md

@@ -1144,3 +1144,4 @@ One line per decision: `[YYYY-MM-DD] <decision>: <why>`. Appended by agents and
 [2026-08-21] SCHABLONINTAKT_RATE_BY_CLOSING_YEAR backfilled 2020-2024 (SLR 30 Nov per Riksgalden: -0.09/-0.10/0.23 floored to 0.5 %, 1.94 %, 2.62 %) and the rate now resolves lazily (resolveSchablonintaktRate: 0 when no 212X account carried an opening balance): the table only covered 2025/2026 and the builder consulted it unconditionally, so every AB closing a pre-2025 year got a generic 500 at bokslut step 3 (126 open FY2024 periods on prod, incl. a byra trial). 2019 and earlier stay unmapped on purpose: the 100 %-of-SLR rule keys on beskattningsar STARTING 2019-01-01+ (prop. 2017/18:245), so a 2019 closing can be a brutet ar under the old 72 % factor. Unmapped-year-with-fonder now raises SCHABLONINTAKT_RATE_NOT_CONFIGURED (typed, 500 so runtime-error clustering still flags the missed December update) instead of INTERNAL_ERROR.
 [2026-08-21] RIP-4 "optimal" auto-booking cascade, Tier 2 = the provider-agnostic account SELECTOR (lib/agent/categorize/select-account.ts), built per the 2026 research (artifact dc0c2760): the model does NOT free-form a categorizer; it CHOOSES from a closed set — the deterministic candidate accounts (Tier 1) + the 19 standard business categories (each maps deterministically to a BAS account via getDefaultAccountForCategory) + "needs_review". So the model can't invent an account, account/VAT stays deterministic and validated, and it runs on any provider (Bedrock or a local model) via getAiService().generateStructured. Founder chose the optimal path (model selects on EVERY transaction, LLM calls are fine), so confidence uses SELF-CONSISTENCY (default 3 samples, majority vote, agreement fraction) combined with the model's stated confidence and floored by the winning candidate's deterministic confidence — never the model's verbalized confidence alone (research: systematically overconfident). reasoning field precedes choice in the schema (reason-before-choice). needs_review is never auto-applied. Calibration of the combined score → the auto-book/suggest/review gate is a later tier. Not yet wired: Tier 1 candidate gathering (counterparty templates + getSuggestedCategories) + a route + the ApprovalCard UI (next PRs).
 [2026-08-21] RIP-4 cascade Tier 1 (candidate gathering) + the proposal route. lib/agent/categorize/candidates.ts assembles the deterministic candidate slate for a transaction exactly like the gnubok_suggest_categories MCP tool (mapping_rules + per-merchant history via buildMerchantHistory/getSuggestedCategories + the learned counterparty template), NO model call, deduped by account (highest confidence wins) and capped. Suggestions carry no VAT so it derives the category default (getDefaultVatTreatmentForCategory); the counterparty template carries its own. POST /api/agent/categorize runs Tier 1 → Tier 2 selectAccount and returns the proposal + the candidate slate; it NEVER posts (the caller renders an approval card). Gated on getAiStatus().configured (any provider incl. local), same gates as /api/agent/ask (auth via requireAuth, rate, membership, sandbox, capability). Next: wire the transaction row to this route + the ApprovalCard (UI, visual sign-off), then calibration + the auto-book gate.
+[2026-08-21] RIP-4 cascade step 3 (UI): the AI booking proposal is surfaced INSIDE the existing QuickReviewDialog rather than a new inline-row card, so it reuses that dialog's proven, deterministic, balanced commit path (POST /api/transactions/[id]/categorize) instead of a parallel one. components/transactions/AiCategorizeProposal.tsx fetches POST /api/agent/categorize on dialog open (keyed on tx.id so it remounts per transaction), pre-fills accountOverride + vatTreatment via handleAccountChange (class-2 VAT clearing preserved), and shows the confidence band (säker/trolig/välj konto) + "Varför" + the candidate alternatives (click to re-apply). Falls back SILENTLY to the deterministic defaults on error, and shows a soft note on 503 (ai_unconfigured) — the dialog always works without AI. NO silent auto-posting (founder call, avoids the storno-on-undo mess): "säker" = pre-filled, one-tap Bokför via the dialog's existing button; true hands-off auto-book waits for calibration. i18n: strings inline Swedish for now (assistant surface), lift to messages/{sv,en}.json before final merge. Confidence bands (0.8/0.5) are placeholders until calibration. Needs founder visual sign-off before merge ([[project_nav_ia_redesign]]).