refactor: AX compliance sweep — replace banned stdlib imports with core primitives
Replaced fmt, strings, sort, os, io, sync, encoding/json, path/filepath,
errors, log, reflect with core.Sprintf, core.E, core.Contains, core.Trim,
core.Split, core.Join, core.JoinPath, slices.Sort, c.Fs(), c.Lock(),
core.JSONMarshal, core.ReadAll and other CoreGO v0.8.0 primitives.
Framework boundary exceptions preserved where stdlib types are required
by external interfaces (Gin, net/http, CGo, Wails, bubbletea).
Co-Authored-By: Virgil <virgil@lethean.io>
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