Function repair_bare_backslashes 

fn repair_bare_backslashes(raw: &str) -> String

Escape every backslash in raw unconditionally. Targets exactly the one corruption shape seen in production — a raw Windows path (C:\Users\...) pasted into a JSON string with NO escaping at all — so every backslash in a still-unparseable row is a literal path separator, never an intentional JSON escape (a document containing even one real \n/\t/\\ escape alongside bare backslashes would imply two different corruption mechanisms touched the same row, which has no evidence and isn’t something this targeted repair needs to handle).

This is deliberately NOT a no-op on already-valid JSON — doubling a genuine \\ pair would over-escape it. That’s fine because the only caller (identity_repair_malformed_secret_refs) already checks serde_json::from_str first and skips rows that parse cleanly; this function must never be called on a value that isn’t already confirmed invalid.

A prior version tried to distinguish “bare” backslashes from “already valid escape sequences” by peeking at the next character (\b, \t, \n, … look like valid escapes). That’s unsound for real Windows paths: a segment like \bob\test starts with \b and \t, which are themselves valid JSON escape shapes, so the heuristic left them un-doubled and silently produced a backspace/tab character instead of the literal path (caught by reagent review on PR #2419).