feat(skills): add review skill with retrospective board format

src/skills/review/SKILL.md

@@ -0,0 +1,136 @@
+---
+name: review
+description: Review any artifact and output results in a Retrospective board format — what is well, what is bad, what should be improved, what to change. Use when the user says "review", "critique", "evaluate", "what's wrong with", "compare", or passes a skill, rule, doc, spec, code, diff, or pull request for assessment. Works on a single artifact, an artifact against a reference, a diff or PR, or two artifacts side by side.
+license: MIT
+tags:
+  - review
+  - quality
+  - retrospective
+metadata:
+  author: Oleg Shulyakov
+  version: "1.0.0"
+  catalog: utility
+  category: productivity
+---
+
+# review
+
+Evaluate any artifact and surface findings as a Retrospective board.
+
+---
+
+## Input Shapes
+
+| Shape | Description | Example |
+| --- | --- | --- |
+| Single artifact | Standalone review, no reference | `review this SKILL.md` |
+| Artifact + reference | Artifact is judged against a ground truth | `review this against the spec` |
+| Diff / PR | Before state is ground truth; changes are under review | `review this pull request` |
+| A vs B | Symmetric comparison, neither is authoritative | `compare these two implementations` |
+
+---
+
+## Workflow
+
+1. **Identify input shape.** Determine which of the four shapes applies from what was provided.
+2. **Triage.** Decide whether a full review is warranted before proceeding.
+3. **Identify artifact type.** Match against the known type registry or fall back to autonomous derivation.
+4. **Derive criteria.** Apply typed criteria for known types; derive autonomously for unknown types.
+5. **Populate quadrants.** Fill each quadrant according to its definition.
+6. **Output the board.**
+
+---
+
+## Triage
+
+Before running a full review, assess whether it is warranted:
+
+- Is the artifact non-empty and in a reviewable state?
+- For diffs: is the change substantive, or a mass rename, whitespace pass, or trivial one-liner?
+- For A vs B: are both artifacts present and comparable?
+
+If triage fails, output a short explanation and stop. Do not produce quadrants.
+
+---
+
+## Artifact Type Registry
+
+| Type | Key criteria |
+| --- | --- |
+| `skill` | Frontmatter completeness, description triggering quality, Gherkin correctness, boundary coverage, workflow clarity |
+| `rule` | Scope, one concern per file, concrete imperatives, conflict with existing rules |
+| `doc / spec` | Clarity, completeness, no stale assumptions |
+| `code` | Correctness, readability, edge case handling |
+| `diff / PR` | Change correctness, regression risk, scope creep, missing tests |
+| `unknown` | Derive criteria autonomously from artifact structure and content |
+
+For **artifact + reference** and **A vs B** shapes, criteria are derived from the comparison axis regardless of type: conformance, gaps, regressions, and structural drift.
+
+---
+
+## Quadrants
+
+Output exactly these four quadrants by default. Caller may override labels or count.
+
+| Quadrant | Definition |
+| --- | --- |
+| **What is well** | What holds up and should be kept as-is |
+| **What is bad** | What is wrong, missing, or harmful and should stop |
+| **What should be improved** | What exists but needs tuning — same direction, better execution |
+| **What to change** | What needs replacement or restructuring — different direction |
+
+The distinction between *improve* and *change*: improve means adjust degree; change means alter kind.
+
+For **A vs B**, quadrants shift to: what A does better, what B does better, what both get wrong, what the stronger candidate should adopt from the weaker.
+
+---
+
+## Boundaries
+
+  Scenario: Artifact is empty or not yet in a reviewable state
+    Given the artifact has no substantive content
+    Then fail triage
+    And explain what is missing before a review can proceed
+    And stop
+
+  Scenario: Diff is non-substantive
+    Given the diff contains only whitespace, renames, or trivial changes
+    Then fail triage
+    And state that no meaningful review is possible for this change
+    And stop
+
+  Scenario: Caller overrides quadrant labels or count
+    Given the caller specifies custom quadrant names or a different number of quadrants
+    Then use the caller-specified quadrants
+    And preserve their definitions as stated
+
+---
+
+## Error Paths
+
+  Scenario: Artifact type is unrecognized
+    Given the artifact does not match any entry in the type registry
+    Then derive criteria autonomously from artifact structure and content
+    And note in the output that autonomous derivation was used
+
+  Scenario: Reference is missing for artifact + reference shape
+    Given the caller implies a reference exists
+    And no reference was provided
+    Then ask for the reference before proceeding
+    And do not fall back to single artifact review silently
+
+  Scenario: A vs B artifacts are not comparable
+    Given the two artifacts are of incompatible types or purposes
+    Then state why comparison is not meaningful
+    And offer to review each independently instead
+
+---
+
+## Verification
+
+  Scenario: Output passes quality check
+    Given a review has been produced
+    Then every finding is tied to a specific artifact element, not a vague impression
+    And improve findings are distinct from change findings — degree vs kind
+    And the output is actionable: each quadrant entry implies a next step
+    And triage was completed before quadrants were populated