Makes `/skill:<name> [args]` work identically under both submission
keybindings, mirroring how free text is already routed during streaming:
- `/skill:foo` + Enter, streaming -> steer queue (interrupt)
- `/skill:foo` + Ctrl+Enter, streaming -> followUp queue
- `/skill:foo` + Enter, idle -> idle prompt
- `/skill:foo` + Ctrl+Enter, idle -> idle prompt (was: literal text)
A single private helper `#invokeSkillCommand(text, streamingBehavior)`
on `InputController` handles the dispatch; the Enter submit handler
calls it with "steer", and `handleFollowUp` calls it with "followUp"
after the compaction short-circuit so a skill typed during compaction
rides the same `queueCompactionMessage` queue as free text.
Behavior deltas vs upstream/main:
- Enter on `/skill:foo` during streaming now steers (was: queued as
followUp). Users who relied on the followUp default can press
Ctrl+Enter -- the same key they already use for free-text follow-ups.
- Ctrl+Enter on `/skill:foo` is new capability; previously the
literal string `/skill:foo ...` was sent as plain followUp text and
the skill was never invoked.
Op: extend
metaphorics
a4258cfc2c