fix(rct): handle reader conditionals

[parth-io]

Support #? reader conditionals in test expectations

Problem

RCT expectations containing reader conditionals (#?(:clj ... :cljr ...)) fail with Conditional read not allowed. This affects .cljc projects that need platform-specific expected values.

;; This fails:
(my-fn args)
;=>
{:result #?(:clj 1 :cljr 2)}

There are two independent issues:

Issue 1: default-read-expectation uses read-string without :read-cond

default-read-expectation calls (read-string expectation-string), which throws on #?.

Fix: (read-string {:read-cond :allow} expectation-string)

This affects both inline (;=> #?(:clj 1 :cljr 2)) and separate-line expectations.

Issue 2: Separate-line expectations are evaluated as standalone test expressions

test-sexpr-zlocs returns all z/sexpr-able? nodes inside a ^:rct/test (comment ...) block, including forms that serve as separate-line expectations:

(+ 1 1)
;=>
2  ;; ← this is ALSO picked up as a standalone test expression

For normal values this is harmless ((eval 2) → 2). But rewrite-clj's ReaderMacroNode.sexpr* converts #?(:clj x :cljr y) into the form (read-string "#?(:clj x :cljr y)"), and evaluating this calls clojure.core/read-string without :read-cond :allow → error.

Fix: Filter out nodes that directly follow an empty result comment — they are expectations, not test expressions. The actual assertion still runs via expectation-data (which traverses forward from the test expression).