docs: add Dart to supported languages table in README (#525)

Dart was added as the 14th supported language in PR #204 but the README
was not updated. Adds Dart row to the supported languages table and
updates the language count from 13 to 14.

Co-authored-by: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

README.md

@@ -375,6 +375,7 @@ GitNexus builds a complete knowledge graph of your codebase through a multi-phas
 | Swift | — | — | ✓ | ✓ | ✓ | ✓ | ✓ | ✓ | ✓ |
 | C | — | — | ✓ | — | ✓ | ✓ | — | ✓ | ✓ |
 | C++ | — | — | ✓ | ✓ | ✓ | ✓ | — | ✓ | ✓ |
+| Dart | ✓ | — | ✓ | ✓ | ✓ | ✓ | — | ✓ | ✓ |
 
 **Imports** — cross-file import resolution · **Named Bindings** — `import { X as Y }` / re-export tracking · **Exports** — public/exported symbol detection · **Heritage** — class inheritance, interfaces, mixins · **Type Annotations** — explicit type extraction for receiver resolution · **Constructor Inference** — infer receiver type from constructor calls (`self`/`this` resolution included for all languages) · **Config** — language toolchain config parsing (tsconfig, go.mod, etc.) · **Frameworks** — AST-based framework pattern detection · **Entry Points** — entry point scoring heuristics
 
@@ -539,7 +540,7 @@ The wiki generator reads the indexed graph structure, groups files into modules
 - [X] Constructor-Inferred Type Resolution, `self`/`this` Receiver Mapping
 - [X] Wiki Generation, Multi-File Rename, Git-Diff Impact Analysis
 - [X] Process-Grouped Search, 360-Degree Context, Claude Code Hooks
-- [X] Multi-Repo MCP, Zero-Config Setup, 13 Language Support
+- [X] Multi-Repo MCP, Zero-Config Setup, 14 Language Support
 - [X] Community Detection, Process Detection, Confidence Scoring
 - [X] Hybrid Search, Vector Index