Add unit tests and knowledge files for BC domain context

- Introduced unit tests for the bc-domain-context implementation, covering various scenarios including filtering by application area, technology mismatches, layer precedence, and conditional applicability.
- Added knowledge files related to finance, including topics such as Chart of Accounts, Codeunit 12, Dimension Management, and VAT on prepayment chains, among others.
- Each knowledge file includes structured metadata and best practices to enhance the domain knowledge available for Business Central tasks.

microsoft/knowledge/finance/dimension-combinations.md

@@ -0,0 +1,28 @@
+---
+bc-version: [1..99]
+domain: finance
+keywords: [dimension-combination, blocked-combination, dimension-matrix, dimension-value-combination]
+technologies: [al]
+countries: [w1]
+application-area: [finance]
+---
+
+# Dimension combinations
+
+## Description
+
+Dimension Combinations (tables 350 — `Dimension Combination`, and 351 — `Dimension Value Combination`) are the guardrail that restricts which dimension values may coexist on the same posting. Table 350 records pair-level rules for two dimensions (typically Global Dimension 1 and Global Dimension 2): the pair may be Blocked, Limited (only specific value pairs allowed), or blank (free). Table 351 records the allowed value pairs under a Limited combination. The check runs during posting via codeunit 408; when a rejected pair arrives on a Dimension Set, posting fails with a specific error naming the blocked combination.
+
+Combinations are the right mechanism for organisational rules like "the Marketing department cannot post to the Factory location" — they enforce once, at post time, across every document type. They are the wrong mechanism for user-input validation (they do not fire until post), and they are often surprising to users who see them for the first time years into a deployment because they were set up once and forgotten.
+
+## Best Practice
+
+When introducing a new blocked combination, run a what-if query against open documents and journal batches first. Existing lines whose dimensions already violate the new rule will fail posting as soon as the rule activates; fix those lines before turning it on.
+
+## Anti Pattern
+
+Using Dimension Combinations to simulate permission checks. They gate posting, not data entry, and they fire in every module — a combination added to enforce a Sales workflow may suddenly block a General Journal entry no one expected.
+
+## Provenance
+
+Migrated from microsoft/BCAppsTriage's `plugins/triage/skills/triage/references/area-knowledge/finance.md` (section: "Dimensions — The #1 Source of Finance Issues") on 2026-04-21.