Add events knowledge domain and review leaf skill

[Jesper Schulz-Wedde (JesperSchulz)]

Summary

Adds a new events knowledge domain covering AL events & subscribers, fully wired into the AL review pipeline. This is increment #3 of the knowledge-seeding initiative, following error-handling and interfaces. The change is purely additive — no contract change (skills/read.md|write.md|do.md|entry.md untouched).

3 atomic articles (each with .good.al + .bad.al samples)

Under microsoft/knowledge/events/:

1. Use the IsHandled pattern to make base behaviour overridable — publisher exposes [IntegrationEvent(false, false)] local procedure OnBeforeX(…; var IsHandled: Boolean); the routine raises it and guards if IsHandled then exit;; a subscriber sets IsHandled := true. Bad: no OnBefore/IsHandled hook (not extensible), or a missing if IsHandled then exit; guard.
2. Publish thin OnBefore/OnAfter integration events to expose extension points — raise thin events at operation boundaries passing var Rec/var IsHandled, with empty publisher bodies. Bad: business logic inside the [IntegrationEvent] publisher body, or no extension points at all.
3. Choose static vs manual subscribers deliberately; bind manual subscribers with BindSubscription — static [EventSubscriber] for always-on; EventSubscriberInstance = Manual + BindSubscription/UnbindSubscription for scoped behaviour. Bad: static subscriber for always-on side effects, or a manual subscriber bound (and held on a SingleInstance global) and never unbound.

Leaf review skill

• microsoft/skills/review/al-events-review.md — modeled on al-error-handling-review.md: 5 sections (Source/Relevance/Worklist/Action/Output), sources the events domain, worklist tokens (IntegrationEvent, BusinessEvent, EventSubscriber, IsHandled, BindSubscription, UnbindSubscription, EventSubscriberInstance, OnBefore, OnAfter, Manual), populated + empty-corpus findings-report examples.

Wiring (additive)

• microsoft/skills/review/al-code-review.md — added the leaf to the frontmatter sub-skills list and the ## Source bullet list; appended , events to the line-6 description parenthetical.
• README.md — leaf-skill count seven → eight; appended , events to the domain list.

API verification

All AL event syntax was verified against Microsoft Learn (not training recall): IntegrationEvent/BusinessEvent attributes and empty publisher bodies; the exact [EventSubscriber(ObjectType, ObjectId, EventName, ElementName, SkipOnMissingLicense, SkipOnMissingPermission)] order; EventSubscriberInstance = Manual;; BindSubscription/UnbindSubscription; and the var IsHandled: Boolean + if IsHandled then exit; convention. Object IDs use 50220–50235 (within the assigned 50220–50239 range; no collision with error-handling 50180–50191 or interfaces 50200–50219). The .al samples are demonstration-only and not compiled by CI.

Validation

• python .github/scripts/validate_frontmatter.py → 0 errors, 0 warnings
• pwsh .github/scripts/Test-KnowledgeIndex.ps1 → PASSED (163 articles, deterministic, full coverage, selection inputs intact)

Notes

• May need a trivial rebase if PR Add interfaces knowledge domain and review leaf skill #42 (interfaces) merges first — both touch the same al-code-review.md sub-skills/Source/description lines and the README count/domain line. Resolve by keeping both leaves and setting the README count to the correct total.

Part of #34.