v0.6.0

fix: address Phase 5a code-review findings

- db/design.py: reuse post/base.py's NodeElemsSelector for REBB/REBC/
  REBR's sub-section ELEMS selector instead of a byte-identical local
  SubSectionElems redeclaration.
- Flag two genuine manual-internal inconsistencies with clarifying
  comments (not bugs -- each endpoint's own section was transcribed
  correctly, but the two source documents disagree with each other or
  with themselves): DCO's SEIS_SYS "Buckling-Restrained Braced Frames"
  is hyphenated while SLRS's FRAME_TYPE spells the same seismic system
  without a hyphen; REBW's SUB_WALL_ID is labeled both "read only" and
  "Required" by the manual's own Parameters table, resolved by
  following the worked example (sent as required client input).

BraceMainBarSpec/ColumnMainBarSpec duplication and DREULT's two
single-field wrapper TypedDicts (raised by the same review pass) were
verified against the manual and left unchanged: REBR's manual section
explicitly states its MAIN_BAR is "similar to REBC but without
USE_CORNER/HOOK_TYPE", and DREULT's COMPONENTS/COLUMN_SECTION_SIZE are
genuinely nested single-key objects per the manual's own JSON Schema.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>