test(tui): update descendant form expectation

[kitlangton]

Why

The mini transport test fails on Linux and Windows after descendant form reads moved under the Session API. The fixture correctly mocks session.form.list, but its final assertion still checks the obsolete top-level form.list method.

What Changes

Update the assertion to match the production call and fixture contract: session.form.list({ sessionID }, { signal }).

Scope

Test-only correction. Runtime behavior is unchanged.

Verification

cd packages/tui
bun run test test/mini/stream-v2.transport.test.ts --test-name-pattern "replaces the client for buffered hydration"
bun typecheck

cd ../..
bun run check

• Focused test passed three consecutive runs.
• Repository lint and typecheck passed.