taurus v0.11.5

Quality — warning-free build

Eliminated all 9 compiler warnings across the codebase:

• Nested /* in block comments (element_index.h, vm.c)
• Unused functions (node_public.c append_path_segment,
  taurus.c taurus_input_has_internal_dtd_subset)
• Const qualifier discard (serialize.c attr caching)
• Scalar initializer style (c14n.c, dtd/validator.c)

The build is now completely -Wall -Wextra clean.

Documentation — remaining work TODOs

• TODO 151: in-place parsing (eliminate buffer copy)
• TODO 152: per-node user_data for FFI wrapper caching (#262)
• TODO 153: high-document-count stress test for CI

Issues closed

• #253, #217, #223, #216 — verified fixed in v0.11.4, closed.