Three parser additions so scripts like `(on click (log me) (trigger foo))`
parse into a single feature with both commands in its body:
1. parse-feat: new cond branch for `paren-open` — advance, recurse
parse-feat, consume `paren-close`. Allows a feature like `(on click
...)` to be grouped in parens.
2. parse-cmd: two new cond branches — on `paren-close` return nil (so
cl-collect terminates at an outer group close), and on `paren-open`
advance / recurse / close. Allows single parenthesized commands like
`(log me)`.
3. cl-collect: previously only recursed when the next token was a
recognised command keyword (`cmd-kw?`), so after `(log me)` the
sibling `(trigger foo)` would end the feature body and re-surface as
a top-level feature. Extended the recursion predicate to also fire
when the next token is `paren-open`.
Suite hs-upstream-core/parser: 9/14 -> 10/14.
Smoke 0-195: 165/195 -> 166/195.