fix(cli): name the typed invocation in the --assert deprecation warning

[Chemaclass]

🤔 Background

Related #1366

bashunit -a reaches the deprecated assert path through the inferred test subcommand, so the warning always named bashunit test --assert, a command the user never ran. The deprecation is correct, the wording pointed at the wrong thing.

💡 Changes

• The warning now quotes the invocation that was typed: bashunit -a, bashunit --assert or bashunit test --assert.
• The dispatcher records whether the subcommand was typed or inferred, which is what the warning needs to tell those apart.
• Acceptance tests cover the three spellings.