fix(resolve): algorithmic and readability improvements

- Replace O(cmds x exts) find_command_protect linear scan with a
  prebaked HashMap built in a single pass over extensions.

- Replace O(n) string-comparison .find() in build_feature_pfn_ranges
  with a direct zip, since both slices are built in matching order.

- Make the --predecessors fixed-point loop incremental: maintain
  command/enum sets across iterations, only extending from newly
  added extensions rather than rebuilding from scratch each pass.

- Remove duplicated work in topo_sort_typedefs cycle fallback that
  built in-degree/reverse-dep structures without deduplication, then
  immediately discarded and rebuilt them with deduplication.

- Introduce a Protection enum to replace the Option<Vec<String>>
  convention (None = unconditional, Some = guarded) used across
  build_ext_type_protections, record_protect, and
  infer_include_protections. Centralizes the lattice merge logic
  in add_extension() and eliminates ~40 lines of duplicated
  match/if-let chains.

- Deduplicate the GL auto-exclude set ("stddef", "khrplatform",
  "inttypes") into a module-level constant shared by
  build_type_list and collect_required_headers.

- Clean up fully-qualified std::collections paths; add VecDeque
  to the import list.

Signed-off-by: Steven Noonan <steven@uplinklabs.net>

Author: tycho