feat(mcp): P2 hygiene — honest category suggestions, skill-reference lint, cadence copy (#882)

* feat(mcp): counterparty-tied category suggestions + no_signal (P2-1)

suggest_categories padded every transaction with a company-wide
category-frequency fallback at <=0.5 confidence — an identical four-way
spread on 20+/24 items that agents correctly reported as pure noise
(agent.feedback). Real signal came from memory atoms and query_journal.

- History is now counterparty-keyed: buildMerchantHistory groups past
  categorized transactions by normalized merchant; the engine only
  surfaces history for THIS transaction's merchant, with provenance
  ('Bokförd N gånger tidigare för denna motpart') and occurrence-scaled
  confidence (0.56 at 1x, capped 0.85). No global padding — an empty
  list is the honest answer.
- The MCP tool returns no_signal_transaction_ids for transactions where
  NO source matched, steering agents to investigate (query_journal)
  instead of pattern-matching on unrelated rows.
- Both callers (REST suggest-categories route + MCP tool) share the new
  helpers, so web UI and agents improve together.

Part of dev_docs/mcp_optimization_plan.md (P2-1).

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

* feat(skills): dangling-reference validation in skills:check + fix 10 dangling links (P2-2)

skills:generate/check now fail when an atom SKILL.md links a
references/*.md that does not exist on disk — a dangling pointer ships
a 404 to every agent that follows it (the weekly-booking-check
incident, agent.feedback).

The validator immediately caught 10 live dangling links in 4 atoms,
three distinct flavors:
- filename typo: swedish-asset-accounting/references/depreciaton.md
  renamed to depreciation.md (the link was right, the file misspelled)
- link mismatch: swedish-e-invoicing linked market-providers-pricing.md;
  the file is market-provider-pricing.md (link fixed)
- unauthored plans: single-shareholder-ab-fmb TODOs and reklambyra's
  'planerad utbyggnad' section used resolvable references/ paths for
  files that were never written — rephrased as plans without paths

Seed migration regenerated (4 atoms bumped, renamed reference child).

Part of dev_docs/mcp_optimization_plan.md (P2-2).

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

* docs(events): align agent-feedback review cadence copy (P2-4)

gnubok_feedback replies 'we aggregate signal weekly'; the event-log
handler comment said quarterly. One of them was lying — weekly wins
(the mcp_optimization_plan triage is the living example).

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

---------

Co-authored-by: Claude Fable 5 <noreply@anthropic.com>

app/api/transactions/suggest-categories/route.ts

@@ -1,6 +1,6 @@
 import { createClient } from '@/lib/supabase/server'
 import { NextResponse } from 'next/server'
-import { getSuggestedCategories, getSuggestedTemplates, type SuggestedCategory, type SuggestedTemplate } from '@/lib/transactions/category-suggestions'
+import { getSuggestedCategories, getSuggestedTemplates, buildMerchantHistory, merchantHistoryFor, type SuggestedCategory, type SuggestedTemplate } from '@/lib/transactions/category-suggestions'
 import { findCounterpartyTemplatesBatch, formatCounterpartyName, toCounterpartyTemplateId } from '@/lib/bookkeeping/counterparty-templates'
 import { requireCompanyId } from '@/lib/company/context'
 import type { Transaction, EntityType } from '@/types'
@@ -48,22 +48,19 @@ export async function POST(request: Request) {
     .eq('is_active', true)
     .order('priority', { ascending: false })
 
-  // Build category history from user's past categorized transactions
+  // Counterparty-keyed history from past categorized transactions — the
+  // suggestion engine only surfaces history tied to the SAME merchant
+  // (global frequency padding produced identical low-confidence spreads).
   const { data: historicalTxns } = await supabase
     .from('transactions')
-    .select('category')
+    .select('category, merchant_name')
     .eq('company_id', companyId)
     .not('is_business', 'is', null)
     .neq('category', 'uncategorized')
     .neq('category', 'private')
     .limit(200)
 
-  const categoryHistory: Record<string, number> = {}
-  if (historicalTxns) {
-    for (const tx of historicalTxns) {
-      categoryHistory[tx.category] = (categoryHistory[tx.category] || 0) + 1
-    }
-  }
+  const merchantHistory = buildMerchantHistory(historicalTxns ?? [])
 
   // Fetch entity type for template matching
   const { data: settings } = await supabase
@@ -84,7 +81,7 @@ export async function POST(request: Request) {
     suggestions[tx.id] = getSuggestedCategories(
       tx as Transaction,
       mappingRules || [],
-      categoryHistory
+      merchantHistoryFor(merchantHistory, (tx as Transaction).merchant_name)
     )
     template_suggestions[tx.id] = await getSuggestedTemplates(tx as Transaction, entityType, mappingRules || undefined)
   }