Add error-handling knowledge domain and review leaf skill

Seed the first new AL knowledge domain toward issue #34: a fully wired
error-handling domain that the review pipeline actually consumes.

- 3 knowledge articles (+ good/bad AL samples):
  - prefer-errorinfo-for-actionable-errors (ErrorInfo Fix-it/Show-it actions)
  - collect-validation-errors-with-errorbehavior (ErrorBehavior::Collect)
  - errortype-internal-vs-client-for-diagnostics (ErrorType Internal vs Client)
- New leaf skill al-error-handling-review.md, modeled on al-performance-review
- Wire the leaf into al-code-review (sub-skills, Source, description)
- README: six -> seven leaf skills

Validated: frontmatter validator clean; knowledge-index check passes
(deterministic, full coverage, selection inputs intact).

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

microsoft/knowledge/error-handling/collect-validation-errors-with-errorbehavior.md

@@ -0,0 +1,26 @@
+---
+bc-version: [all]
+domain: error-handling
+keywords: [collectible-errors, errorbehavior, collect, getcollectederrors, hascollectederrors, validation, batch]
+technologies: [al]
+countries: [w1]
+application-area: [all]
+---
+
+# Collect validation errors with ErrorBehavior::Collect and handle the collected list
+
+## Description
+
+By default a procedure stops on the first `Error`, so a user fixing ten bad rows must rerun the operation ten times. The collectible-errors feature postpones error handling to the end of the call: a procedure attributed `[ErrorBehavior(ErrorBehavior::Collect)]` keeps running as errors occur and gathers them, so all failures can be presented together. The collected errors are read with `HasCollectedErrors()` and `GetCollectedErrors()` (which returns a `List of [ErrorInfo]`); `ClearCollectedErrors()` empties the buffer. This is a platform mechanism most LLMs are unaware of — they reach for a manually concatenated `Text` buffer or a temporary error table instead.
+
+## Best Practice
+
+Mark the orchestrating procedure `[ErrorBehavior(ErrorBehavior::Collect)]` and run each item's validation so one failure doesn't abandon the rest — typically by calling the per-item routine through `Codeunit.Run`. When the run finishes, inspect `HasCollectedErrors()` and surface `GetCollectedErrors()` to the user as a single list. Always handle the collected errors yourself: the platform's own guidance is that any errors still in the collected list when the procedure ends are concatenated into one dialog, which is hard for users to read.
+
+See sample: `collect-validation-errors-with-errorbehavior.good.al`.
+
+## Anti Pattern
+
+Two shapes signal trouble. The first is hand-rolled accumulation — appending messages to a `Text` variable and showing them at the end — which reimplements the platform feature, loses each error's `ErrorInfo` structure, and skips telemetry classification. The second is applying `[ErrorBehavior(ErrorBehavior::Collect)]` but never calling `HasCollectedErrors`/`GetCollectedErrors`, so every collected error spills into the platform's concatenated end-of-procedure dialog. Detection: a `Collect` attribute with no matching `GetCollectedErrors` call, or a per-row loop that builds an error string by concatenation.
+
+See sample: `collect-validation-errors-with-errorbehavior.bad.al`.