Seed web-services (API v2) knowledge domain

[JesperSchulz]

Seeds a new web-services knowledge domain covering API endpoint design and behavior (API v2 / API pages), plus a matching review leaf skill and the routine wiring.

Scope / de-duplication

This domain deliberately covers API endpoint design and behavior only. It excludes topics already owned by other domains, to avoid duplication:

• API entity naming, camelCase properties, DelayedInsert, and the vX.Y version-string format are owned by the style domain.
• The ReadIsolation-vs-LockTable mechanic (lock blast-radius / read performance) is owned by the performance domain. The committed-data article here is framed strictly as the endpoint's data-consistency contract (what a consumer receives), not as a locking/performance concern.

Knowledge articles (6)

Each is a .md with sibling .good.al / .bad.al samples, domain: web-services, unique object IDs in the 50340–50357 range (gaps at 50342/50343/50346/50347 left from the trimmed articles; no renumbering, no collisions):

1. set-required-api-page-properties — a PageType = API page must declare APIPublisher, APIGroup, APIVersion, EntityName, EntitySetName, and SourceTable.
2. expose-systemid-as-the-api-key — ODataKeyFields = SystemId + field(id; Rec.SystemId) for stable addressing.
3. expose-only-committed-data-from-api-reads — Rec.ReadIsolation := IsolationLevel::ReadCommitted in OnOpenPage so the endpoint returns only committed data (bc-version [22..]).
4. expose-operations-as-bound-actions — [ServiceEnabled] bound actions via WebServiceActionContext, not side-effecting status flags.
5. version-apis-by-adding-not-mutating-published-versions — add a new APIVersion alongside the published one instead of mutating it in place.
6. disable-write-operations-on-read-only-api-pages — InsertAllowed/ModifyAllowed/DeleteAllowed = false (and Editable = false).

New leaf skill

• microsoft/skills/review/al-web-services-review.md — modeled on al-error-handling-review.md, sourced from domain: web-services knowledge.

Wiring

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

Validation

• python .github/scripts/validate_frontmatter.py → 0 errors / 0 warnings.
• pwsh -File .github/scripts/Test-KnowledgeIndex.ps1 → PASSED (166 articles, deterministic, full coverage, selection inputs intact, no object-ID collisions). The knowledge index is generated, not committed.

Note on wiring conflicts

A routine wiring conflict is expected with other open leaf-domain PRs (#42 / #43 / #44) in al-code-review.md and README.md. Resolution: keep ALL leaves, and set the README leaf count = base + number of merged leaf domains.

Part of #34.