feat: add unified-review workflow (scoring tools + skill)

Adds the unified-review integration that fuses CRG graph context with the
ai-code-review scoring methodology and gstack-review fix-first workflow:

- scoring.py: objective Layer-2 metrics (sql_risk, exception_coverage,
  redundancy_rate, high_risk_density, vulnerability_risk) with
  good/warn/fail grades, plus dedupe_findings (fingerprint merge,
  multi-source confidence boost, PR quality score) and report data builder
- tools/scoring_tools.py + main.py: three new MCP tools
  (score_review_tool, dedupe_findings_tool, generate_report_tool)
- assets/report-template.html: self-contained HTML report template
- skills.py + skills/unified-review/: new read-only unified-review skill
  with language/manual-review/specialist checklists
- docs and CHANGELOG updated; tests added (test_scoring, test_report,
  test_unified_review) and test_skills updated for 5 skills

docs/architecture.md

@@ -27,6 +27,8 @@
 │  │  ├── Communities: list, get, architecture  │              │
 │  │  ├── Analysis: detect_changes, refactor,   │              │
 │  │  │   apply_refactor, hotspots, gaps        │              │
+│  │  ├── Scoring: score_review, dedupe_        │              │
+│  │  │   findings, generate_report             │              │
 │  │  ├── Wiki: generate, get_page              │              │
 │  │  └── Multi-repo: list_repos, cross_search  │              │
 │  └────────────────┬───────────────────────────┘              │
@@ -34,16 +36,21 @@
                     │
         ┌───────────┼───────────────┐
         ▼           ▼               ▼
-   ┌─────────┐ ┌─────────┐  ┌─────────────┐
-   │ Parser  │ │  Graph  │  │ Incremental │
-   │         │ │  Store  │  │   Engine    │
-   └────┬────┘ └────┬────┘  └──────┬──────┘
-        │           │              │
-        ▼           ▼              ▼
-   Tree-sitter   SQLite DB      git/svn diff
-   grammars      (.code-review- subprocess
-                 graph/
-                 graph.db)
+    ┌─────────┐ ┌─────────┐  ┌─────────────┐
+    │ Parser  │ │  Graph  │  │ Incremental │
+    │         │ │  Store  │  │   Engine    │
+    └────┬────┘ └────┬────┘  └──────┬──────┘
+         │           │              │
+         ▼           ▼              ▼
+    Tree-sitter   SQLite DB      git/svn diff
+    grammars      (.code-review- subprocess
+                  graph/
+                  graph.db)
+
+    Scoring module (code_review_graph/scoring.py) sits on top of the
+    GraphStore and reads changed files + git history to compute the
+    objective review metrics consumed by the unified-review skill and the
+    score_review / dedupe_findings / generate_report MCP tools.
 ```
 
 ## Data Flow