Function backup_and_write_json

src/agents/mod.rs:729–732

Best-effort "back up and write" for uninstall paths. Mirrors the install pattern (`backup_config_file` then `safe_write_json_file`) but swallows errors so the rest of the uninstall can continue. Returns `true` when the new content reached disk. Issue #63: every config rewrite must leave a `.bak` so the user can recover if anything goes wrong.

(path: &Path, value: &serde_json::Value)

/// Issue #63: every config rewrite must leave a `.bak` so the user can
/// recover if anything goes wrong.
pub fn backup_and_write_json(path: &Path, value: &serde_json::Value) -> bool {
    let backup = backup_config_file(path).ok().flatten();
    safe_write_json_file(path, value, backup.as_deref()).is_ok()
}

/// Finds the tracedecay binary path.
///