Scope table filtering: support scoped Table Filter, refine matching and loading behavior

[koianaoki]

Motivation

• Improve the Explorer tree filter to support a scoped "Table Filter" that searches only inside a Tables subtree without affecting the main connection/database behavior.
• Prevent unnecessary loading of folders during global searches while allowing the Table Filter to load and search table folders.
• Make node traversal and match selection consistent between scoped and unscoped filters so cursor movement and activation behave correctly.

Description

• Added a scoped filter flag via self._tree_filter_scope_path and conditioned loading, counting, matching, and visibility logic on that flag in TreeFilterMixin.
• Introduced _tree_filter_should_descend_node to control whether children are inspected during filtering and tightened _tree_filter_can_match_node to restrict default matches to connection/database types while scoped filters match tables only.
• Updated _update_tree_filter, _find_matching_nodes, _count_all_nodes, _ensure_tree_filter_search_nodes_loaded, _tree_filter_node_has_pending_load, _apply_filter_to_tree, _jump_to_current_match, and action_tree_filter_accept to handle scoped vs unscoped behavior correctly, and preserved main filter behavior for activation and cursor restoration.
• Added protocol declaration for _tree_filter_should_descend_node in ExplorerActionsProtocol and adjusted label/visibility handling to preserve highlight and pending-load semantics.
• Tests adjusted and new tests added in tests/ui/test_tree_filter_tables_scope.py to validate scoped searches, loading behavior, and accept/activation behavior.

Testing

• Ran the unit tests in tests/ui/test_tree_filter_tables_scope.py which include expanded scenarios for scoped table filtering, folder loading behavior, and accept/activation; all tests passed.
• Exercised TreeFilterMixin behaviors for both scoped (action_table_filter) and unscoped (action_tree_filter) flows via the test suite, and assertions for cursor, selection, loading calls, and visibility succeeded.

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Codex Task