Kotlin Multiplatform `expect`/`actual` calls resolve to nothing

## What is wrong

Kotlin Multiplatform code declares `expect class Platform()` in shared code and an
`actual class Platform` per platform. With Kotlin support, both rows count as definitions. A call
from any other directory therefore sees two candidates, neither in its own file nor its own
directory, and is declined — so no edge is built. Fixing it gives every Kotlin Multiplatform
codebase its shared-code call graph back.

## The evidence

On the head of the Kotlin support PR (#126), `--callees` answers a bare `count="0"`, as if nobody
made the call at all. PR #136 (now on `main`) at least counts the call as declined, but it still
binds to nothing.

The cost was measured on ktor: of the 138 Kotlin call pairs that #126's bodyless-type rule moved,
**48 sit on `expect`/`actual` names**.

## Size

**Medium.** The change is one extracted bit (a free padding byte in `Symbol` is already measured),
one predicate change, a parser and cache version bump with their mirrors and pins, a new section in
`test/kotlincheck.sh`, and a ktor measurement.

## Prerequisite

PR #126 (Kotlin support), still open. The prompt describes the code #126 adds and explains how to
confirm the integrated head is in place. The arms it describes go into `test/kotlincheck.sh`, which
#126 adds.

## Where to start

`prompts/help-wanted/kotlin-expect-actual.md` is a self-contained prompt for a coding agent. It
covers why this matters with the measurements, how extraction, the decl/def collapse and resolution
work, a three-file reproduction with recorded output, the design space (a recommended start, an
alternative, and what is rejected), the non-negotiables, red-first acceptance arms, the known traps,
and what the fix PR's description must contain. Like every prompt in `prompts/`, **it ends by
writing a plan and stopping** — a maintainer agrees the plan before any code is written.

Comment here to claim it.

Start with prompts/help-wanted/kotlin-expect-actual.md, then inspect the Kotlin support from PR #126 and its three-file reproduction. Run the red-first acceptance arms in test/kotlincheck.sh and review the parser and cache version mirrors and pins. Done means expect/actual calls resolve and the recorded ktor measurement is updated.

Written by the indexing model from the issue text.