fix(tree): make findNode/getParentNode null-tolerant

[Aias00]

What

Tree store actions can run while treeData is legitimately null during initialization, refresh, or after clearing the store. The previous lookup helpers dereferenced the tree and also claimed a non-null return type even when a node was not found.

Fix

• Move the recursive lookup logic into treeNodeLookup.ts.
• Accept nullable tree input and return TreeNodeData | undefined from findNode and getParentNode.
• Guard all affected rename, delete, close-connection, and refresh call sites with explicit fallback behavior.
• Refresh the full tree when a parent node cannot be located.
• Avoid splice(-1, 1) when the target datasource is absent.
• Add focused lookup tests for null trees, missing keys, nested matches, and parent lookup.

Verification

• yarn test:tree-node-lookup
• yarn test:tree-data-update
• ESLint on all changed TypeScript files with zero warnings
• yarn build:web:community

Fixes #2424

[Copilot]

Pull request overview

Fixes a frontend tree-store crash by making tree traversal helpers resilient to treeData === null during initial load / refresh windows, preventing null.length runtime errors.

Changes:

• Add null guards to getParentNode’s iteration to avoid dereferencing tree.length when treeData is null.
• Add null guards to findNode’s iteration for the same null-tree scenario.

Suppressed comments (1)

chat2db-community-client/src/utils/index.ts:396

• The recursive branch calls getParentNode(key, node.children) twice, which doubles the traversal work for every branch and makes the logic harder to read. Cache the recursive result in a local variable and reuse it.

      if (node.children.some((item) => item.key === key)) {
        finalNode = node;
      } else if (getParentNode(key, node.children)) {
        finalNode = getParentNode(key, node.children);
      }

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[openai0229]

Reviewed after the nullable-contract and call-site fixes. The focused lookup tests, affected-file ESLint, and full Community frontend build pass locally.