taurus v0.11.2

Fix — DOCTYPE PUBLIC/SYSTEM identifiers (#253)

direct_parse's DOCTYPE handler extracted the name and internal
subset but silently dropped PUBLIC/SYSTEM external identifiers.
After the name scan, the parser skipped straight to [ or >,
bypassing the external ID declarations.

Fix: re-scan the region between name and [ / > for PUBLIC or
SYSTEM keywords followed by quoted identifiers. Set public_id /
system_id on the DOCTYPE node. Verified with all DOCTYPE variants:
bare name, SYSTEM, PUBLIC, PUBLIC+subset, name+subset.

Fix — iterative tree freeze (#256, deeper investigation)

The v0.11.1 fix (clearing g_current_document) addressed the
thread-local stale pointer but the crash persisted for some inputs.
taurus_node_freeze was recursive — under tight parse loops
on deeply nested documents, the unbounded recursion could exhaust
the thread stack.

Fix: converted to an iterative depth-first walk with a fixed
256-deep explicit stack, eliminating the stack-overflow crash
vector entirely.