The `press` command was not parsing modifier+key chords (e.g.
`Control+a`, `Shift+Enter`). It sent the raw string as a single key
name, so CDP never applied the modifier — and the `text` field caused
the literal character to be inserted instead of triggering the shortcut.
Two changes:
1. `actions.rs` — add `parse_key_chord()` to split inputs like
`Control+Shift+a` into the base key (`a`) and a CDP modifier
bitmask (Alt=1, Ctrl=2, Meta=4, Shift=8), then call
`press_key_with_modifiers` instead of `press_key`.
2. `interaction.rs` — suppress the `text` field in `keyDown`/`keyUp`
events when Control or Meta modifiers are active, so the browser
treats them as command chords rather than text input.
Includes unit tests for the chord parser covering plain keys, single
modifiers, multi-modifier combos, modifier aliases, and edge cases.
Co-authored-by: ctate <366502+ctate@users.noreply.github.com>
