Bound suggestion-store reads before full deserialize

[Widthdom]

Problem

src/CodeIndex/Cli/SuggestionStore.cs reads the entire suggestion store JSON file with File.ReadAllText and deserializes the whole record list at once.

Impact

A large or corrupt local suggestion history can consume excessive memory or make suggestion commands fail before they can recover or prune the store.

Expected

Apply a file-size cap before full deserialization, report a bounded recovery error for oversized stores, and prefer streaming for read-only listing or query paths where possible.

[Widthdom]

Work started on branch fix-issue2844-2856-2857-2870-2858-2871-2872-2867.