`mosaic yolo <runtime>` forwarded `cmd.args` (which Commander populates with
the declared `<runtime>` positional) to the underlying CLI. For the claude
runtime that meant argv included the literal string "claude" as an initial
positional argument, which Claude Code interpreted as the first user message.
As a secondary consequence, the mission-auto-prompt path was also bypassed
because `hasMissionNoArgs` saw a non-empty args list.
Refactor the runtime subcommand wiring into an exported
`registerRuntimeLaunchers(program, handler)` factory with a
`RuntimeLaunchHandler` type so the commander integration is unit-testable
without spawning subprocesses. Slice the declared positional off `cmd.args`
in the yolo action before forwarding.
Adds `packages/mosaic/src/commands/launch.spec.ts` with 11 regression tests
covering all four runtimes (claude, codex, opencode, pi) for both `<runtime>`
and `yolo <runtime>` paths, excess-args forwarding, and invalid-runtime
rejection. The critical assertion blocks the regression: yolo parses must
forward `extraArgs = []`, not `[runtime]`.
Fixesmosaicstack/stack#454
Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>
