feat(L06): add control flow and program counter card

doc/assets/control-flow.svg

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+<svg xmlns="http://www.w3.org/2000/svg" width="600" height="210" viewBox="0 0 600 210" role="img" aria-labelledby="title desc"><title id="title">Wybór następnego PC</title><desc id="desc">Komparator i immediate wpływają na multiplekser wybierający PC plus cztery, cel gałęzi lub cel skoku.</desc><defs><marker id="a" markerWidth="9" markerHeight="9" refX="8" refY="3" orient="auto"><path d="M0 0L0 6L8 3z" fill="#16324a"/></marker></defs><rect width="600" height="210" fill="#f7fafc"/><g fill="#eef3f7" stroke="#16324a" stroke-width="2"><rect x="20" y="58" width="130" height="84" rx="10"/><rect x="190" y="58" width="130" height="84" rx="10"/><rect x="360" y="58" width="100" height="84" rx="10"/><rect x="500" y="58" width="80" height="84" rx="10"/></g><g font-family="system-ui,sans-serif" text-anchor="middle" fill="#16324a"><text x="85" y="90" font-size="17" font-weight="700">COMPARE</text><text x="85" y="117" font-size="14">taken</text><text x="255" y="90" font-size="17" font-weight="700">IMM B / J</text><text x="255" y="117" font-size="14">PC-relative</text><text x="410" y="90" font-size="17" font-weight="700">NEXT MUX</text><text x="410" y="117" font-size="14">+4 / target</text><text x="540" y="90" font-size="17" font-weight="700">PC</text><text x="540" y="117" font-size="14">register</text></g><g stroke="#16324a" stroke-width="3" marker-end="url(#a)"><path d="M150 100H180"/><path d="M320 100H350"/><path d="M460 100H490"/></g><text x="300" y="184" font-family="system-ui,sans-serif" text-anchor="middle" font-size="15" fill="#b6402d">jump → branch_taken → pc+4</text></svg>