Introduce super-skill composition; refactor al-code-review into super + two leaves

DO contract (skills/do.md)
- New 'sub-skills' optional frontmatter field on action skills: when
  present and non-empty, the skill is a super-skill that composes
  other action skills.
- New 'Composition (super-skills)' section covering section
  interpretation, outcome rollup, summary aggregation, and suppression
  scope.
- Output schema gains three optional fields: 'from-sub-skill' on each
  finding, top-level 'sub-results[]' carrying nested findings-reports,
  and top-level 'skipped-sub-skills[]'.
- Super-skills MUST NOT filter sub-skills by task content; leaves own
  task-level applicability and signal via outcome.
- Findings from a failed sub-skill MUST NOT flow into the parent's
  findings[] or counts, consistent with DO's rule that consumers
  ignore a failed skill's findings. Reports are still preserved in
  sub-results[] for traceability.
- Rolled-up non-citation finding ids MUST be prefixed with the sub-
  skill id to prevent collisions across sub-skills. Citation-based
  ids are already unique via repo path and are not rewritten.
- Outcome rollup rules updated: 'partial' covers S = {partial},
  {partial, partial}, and {partial, failed}. Empty worklist rolls up
  to 'not-applicable' with outcome-reason.
- Nested super-skills are not permitted in v1.

Reference skills (microsoft/skills/)
- al-code-review.md rewritten as the canonical super-skill: lists
  al-performance-review and al-security-review as sub-skills, orch-
  estrates invocation, aggregates output, and includes a worked
  rolled-up JSON example plus the empty-corpus rollup.
- al-performance-review.md added as a leaf reference skill for the
  performance knowledge domain.
- al-security-review.md added as a leaf reference skill for the
  security knowledge domain.
- Both leaves retain the leaf-level rules validated in the prior
  pass: partial-context message requirement, worklist-scoped
  suppression, application-area semantics, and the platform-guarantee
  threshold for blocker severity.

README updated to describe leaf vs super-skill and link all three
reference skills.

Two rubber-duck passes tightened the contract and caught schema
violations in the worked examples before commit.

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

microsoft/skills/al-performance-review.md

@@ -0,0 +1,126 @@
+---
+kind: action-skill
+id: al-performance-review
+version: 1
+title: AL performance review
+description: Reviews AL source changes against performance guidance from BCQuality.
+inputs: [pr-diff, file-path]
+outputs: [findings-report]
+bc-version: [26..28]
+technologies: [al]
+countries: [w1]
+application-area: [all]
+---
+
+# AL performance review
+
+Reviews AL source changes against the `performance` knowledge domain in BCQuality and emits a findings report. This is a leaf action skill: it invokes no sub-skills. It is one of the skills composed by `al-code-review`.
+
+An orchestrator invokes this skill with either a `pr-diff` (the standard PR-review entry point) or a `file-path` (single-file review). The skill produces a single JSON document conforming to the DO output contract.
+
+## Source
+
+Collect all knowledge files under `*/knowledge/performance/**/*.md`, across every enabled layer (`/microsoft/`, `/community/`, `/custom/`). Relevance trims the result to the subset that applies.
+
+## Relevance
+
+Apply the frontmatter matching rules defined in READ (*Frontmatter matching semantics*) against the task context:
+
+- `bc-version` — the target BC version from the PR branch's `app.json` or the orchestrator-supplied version. If unavailable, the dimension is `unknown`.
+- `technologies` — `[al]`.
+- `countries` — the countries declared in the consuming app's `app.json`. Default to the orchestrator's configured context; if absent, `unknown`.
+- `application-area` — the union of application areas declared by the changed objects. Pass the actual set; do not substitute `[all]`. If the area cannot be determined from the changes, the dimension is `unknown`.
+
+Discard files that are not applicable. Retain conditionally applicable files (any dimension `unknown`) only when the orchestrator's configuration permits them; findings derived from those files MUST have `confidence` no higher than `medium`, AND the finding's `message` MUST name the dimension or dimensions that were unknown.
+
+## Worklist
+
+Narrow the relevant files to the subset that applies to the changes under review. For each relevant file, compute overlap against:
+
+- The changed AL object names and types — especially tables, pages with SourceTable bindings, reports, queries, and codeunits performing record iteration.
+- The changed procedures and triggers, weighted toward those that perform loops, Find/FindSet/FindFirst calls, CalcFields, CalcSums, FlowField access, or cross-table navigation.
+- Tokens extracted from the diff that relate to data access (SetRange, SetFilter, SetLoadFields, SetCurrentKey, FindSet, Repeat…Until, CalcFields, CalcSums).
+
+A file enters the candidate worklist when its `keywords` intersect the extracted tokens or its topic (derived from filename and Description) matches a changed object type.
+
+Once the candidate worklist is known, resolve layer-precedence conflicts per READ. Drop lower-precedence files whose normative guidance (`## Best Practice` or `## Anti Pattern`) directly contradicts a higher-precedence candidate, and record each dropped file in `suppressed` with `reason: "layer-precedence"`. Files that would have been candidates but are hidden because their layer is disabled in consumer configuration are recorded with `reason: "configuration"`. Files that never became candidates are NOT recorded in `suppressed`.
+
+When the post-conflict worklist is empty because no applicable performance knowledge exists, or because configuration suppressed every candidate, emit `outcome: "no-knowledge"`. When the worklist is empty because no applicable performance knowledge matched the changes, emit `outcome: "completed"` with an empty `findings` array.
+
+## Action
+
+For each worklist entry, evaluate the diff against the file's `## Best Practice` and `## Anti Pattern` sections. Emit findings as follows:
+
+- When the diff contains a clear match for an Anti Pattern, emit a finding with severity `major` or `blocker`, a message summarizing the anti-pattern, `location` pointing to the offending line or range, and a `references` entry pointing to the knowledge file. Use `blocker` only when the knowledge file states the anti-pattern violates a platform-level guarantee (for example, documented query timeouts or transaction size limits). When the file does not make such a claim, the ceiling is `major`.
+- When the diff contains code that contradicts a Best Practice without being a full anti-pattern, emit `minor` with the same reference shape.
+- When the skill cannot detect a violation but the file is clearly applicable to the change, emit `info` citing the file. Repository-wide observations MAY omit `location`.
+
+Set `confidence` to:
+
+- `high` when the detection is based on an unambiguous pattern match (identifier, syntax, object type).
+- `medium` when detection relies on heuristics or when any frontmatter dimension was `unknown`.
+- `low` when the finding is an advisory derived only from applicability.
+
+Outcome selection:
+
+- `completed` — the skill evaluated every worklist item; default when the skill finishes normally, including when the resulting `findings` array is empty.
+- `no-knowledge` — no applicable performance knowledge survived Source, Relevance, configuration filtering, and conflict resolution. `findings` is empty.
+- `not-applicable` — the task context lacks an AL dimension (no AL changes in the diff, or `technologies` filter rejected the task).
+- `partial` — a time or token budget was hit before the worklist was exhausted. `summary.coverage` reflects the evaluated subset; `outcome-reason` explains the cause.
+- `failed` — an unrecoverable error occurred. `outcome-reason` is required.
+
+## Output
+
+Output conforms to the DO output contract. A populated example:
+
+```json
+{
+  "skill": { "id": "al-performance-review", "version": 1 },
+  "outcome": "completed",
+  "summary": {
+    "counts": { "blocker": 0, "major": 1, "minor": 0, "info": 1 },
+    "coverage": { "worklist-size": 2, "items-evaluated": 2 }
+  },
+  "findings": [
+    {
+      "id": "microsoft/knowledge/performance/filter-before-find.md",
+      "severity": "major",
+      "message": "FindSet is called on a record variable without any prior SetRange/SetFilter. This forces a full-table scan.",
+      "location": {
+        "file": "src/Sales/PostingRoutines.Codeunit.al",
+        "line": 140,
+        "range": { "start-line": 140, "end-line": 144 }
+      },
+      "references": [
+        { "path": "microsoft/knowledge/performance/filter-before-find.md" }
+      ],
+      "confidence": "high"
+    },
+    {
+      "id": "community/knowledge/performance/use-setloadfields.md",
+      "severity": "info",
+      "message": "Posting routine iterates ledger entries; consider whether SetLoadFields applies per the linked guidance.",
+      "references": [
+        { "path": "community/knowledge/performance/use-setloadfields.md" }
+      ],
+      "confidence": "low"
+    }
+  ],
+  "suppressed": []
+}
+```
+
+The empty-corpus case — BCQuality's state until performance knowledge files land — produces:
+
+```json
+{
+  "skill": { "id": "al-performance-review", "version": 1 },
+  "outcome": "no-knowledge",
+  "summary": {
+    "counts": { "blocker": 0, "major": 0, "minor": 0, "info": 0 },
+    "coverage": { "worklist-size": 0, "items-evaluated": 0 }
+  },
+  "findings": [],
+  "suppressed": []
+}
+```