#406 (split app.js → tabs/flow/common) closed; the migration is
done — the 'moved to ./flow.js' / 'pre-step-2 this wiring lived
in the broker-terminal IIFE' commentary is git-history, not
present-state docs. #408 (split flow messages from main sse) also
closed; the 'will give /index.html its own stream' line was
forward-looking design that didn't ship that way. Comments
tightened to describe what the code does today; the section
headers, behaviour notes, and reconnect-rationale all stay
intact.
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