Date remaining draft links in the 2026-07-28 spec tree

The cut-release promote step rewrote /specification/draft/ links but
left /docs/draft/ and schema/draft/ links untouched in the promoted
spec tree, so 13 links in docs/specification/2026-07-28/ still pointed
at the living draft tiers. Date all 13 to 2026-07-28, matching the
hand-cut 2025-11-25 snapshot, and extend the workflow so future cuts
rewrite both patterns plus the changelog compare link.

Fixes #3160

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01DrwuUqBvFfzvqAFmefi7pU