feat: Implement association tree for LSP-based code relationship discovery

- Add `association_tree` module with components for building and processing call association trees using LSP call hierarchy capabilities.
- Introduce `AssociationTreeBuilder` for constructing call trees from seed locations with depth-first expansion.
- Create data structures: `TreeNode`, `CallTree`, and `UniqueNode` for representing nodes and relationships in the call tree.
- Implement `ResultDeduplicator` to extract unique nodes from call trees and assign relevance scores based on depth, frequency, and kind.
- Add unit tests for `AssociationTreeBuilder` and `ResultDeduplicator` to ensure functionality and correctness.

codex-lens/lsp-servers.json

@@ -9,8 +9,20 @@
       "extensions": ["py", "pyi"],
       "command": ["pyright-langserver", "--stdio"],
       "enabled": true,
-      "initializationOptions": {},
-      "settings": {}
+      "initializationOptions": {
+        "pythonPath": "",
+        "pythonPlatform": "",
+        "pythonVersion": "3.13"
+      },
+      "settings": {
+        "python.analysis": {
+          "typeCheckingMode": "standard",
+          "diagnosticMode": "workspace",
+          "exclude": ["**/node_modules", "**/__pycache__", "build", "dist"],
+          "include": ["src/**", "tests/**"],
+          "stubPath": "typings"
+        }
+      }
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