Preserve keyword calls in bounded expression reconstruction

[EiNSTeiN-]

I am opening this PR to reconstruct named-argument calls in pycdc's bounded expression walker while preserving their enclosing call. The code below currently produces incomplete output:

def select(value, build, other):
    return build("reject" if value else "accept", amount=0)

The incorrect output calls None on one branch:

def select(value, build, other):
    if value:
        return build("reject", amount=0)
    return None("accept", amount=0)

The main parser supports named calls, but its bounded expression walker lacks CALL_KW support. The added handler reads the keyword-name tuple, checks its string entries and argument counts, separates positional from named arguments, and consumes the callable/NULL marker in the existing stack convention. This retains keyword names and argument evaluation order instead of turning the call into an unparseable region or a wrong positional call.

The ternary merger must also retain a keyword-bearing call when merging its argument values. It matches keyword names and order and includes their values alongside positional values in its single-slot merge. This supports both a conditional positional argument and a conditional keyword argument:

build("prefix", amount=0 if value else 1)
build(0 if value else 1, amount=value)

An arm-local callable or argument prefix must not be mistaken for a value preloaded before the condition. The bounded merger declines that shape rather than moving callable resolution or argument evaluation across the truth test.

CALL_KW is introduced in Python 3.13; the added decoding applies to that opcode layout.