Add a placement table to the Definition section: which `groupTree`
position a Chat Node declares for an opening human input, another Turn
input, a Turn notice outside folding, an independent folded row, and
ordinary process content, with links to the contract and the built-in
positions, and a pointer to `exclusive` claims.
State in the `exclusive` JSDoc and the Conversation reference that the
claimed target's fallback does not run and that a fallback's own claim
has no effect. Reword the `input` position as the Turn's opening input
and separate the finalized-answer exemption from position-less
`assistant-step` rows. Point both package READMEs at the claim and the
group-tree positions.
A match result may set `exclusive: true`. The assembler evaluates every
match of an event before accepting any, so a claim is independent of
registration order: other Definitions of the claimed target build no
Context for the event and the target's fallback does not run, while
Definitions of other targets and target-less Definitions still receive
it. Two claims on one target, or a claim without a target, throw.
imccyu