Document the weak-parent ownership trap at the public entry points: parseTree
and readTree now state that a tree (or ownerDocument) must be held while using
any node inside it, that TreeNode has no internal synchronization (confine to
one thread or actor), and that the immutable Sendable Node projection is the
way across concurrency boundaries; the TreeNode class doc carries the same
contract. QualifiedName's malformed-colon fallback (':local', 'prefix:', '::'
stay whole and unprefixed), already implemented, is now documented on init
and locked by a test.
Closes#114
Mihaela Mihaljevic
363a88070a