Tests, examples and run lines use placeholder credentials (#332)

Test fixtures pass "player"/"secret"; the run lines in `.cargo/config.toml`, the protocol
examples and the auth and world binaries show placeholders; the SRP probe example takes
--user and --pass instead of defaulting them. Built on macOS.

Co-Authored-By: Claude Opus 5.5 (1M context) <noreply@anthropic.com>

crates/benilla-protocol/src/bin/benilla-auth.rs

@@ -1,6 +1,6 @@
 //! `benilla-auth`: SRP6 logon against a vanilla realmd, printing the realm list.
 //!
-//! Example: `cargo run --bin benilla-auth -- one pone localhost`
+//! Example: `cargo run --bin benilla-auth -- <account> <password> localhost`
 
 use anyhow::Result;
 use clap::Parser;

crates/benilla-protocol/src/bin/benilla-world/main.rs

@@ -1,7 +1,7 @@
 //! `benilla-world`: logs in to realmd, enters the world server as a character, and tallies the
 //! updates it pushes; the `--<probe>` flags live-verify one wire each.
 //!
-//! Example: `cargo run -p benilla-protocol --bin benilla-world -- one pone localhost`
+//! Example: `cargo run -p benilla-protocol --bin benilla-world -- <account> <password> localhost`
 //!
 //! An account with no character gets a Human Warrior (`--create <name>`). The world address
 //! defaults to the realm list's (`--world` overrides).