DOCFIX-150: Stage 0 ratification -- D-100..D-110 ADOPTED ...

Operator ruled live on the buildout design's 6 redline items and on each of
D-100 through D-110 individually.

Redline rulings: Ceph size=3 by default (size=2 only as an explicit,
logged Phase-0 fallback); tc netem same-metro lean confirmed; D-102 folds
into D-101, D-109 stays standalone; metal-admin GAINS a ULA leg (reverses
the design's own stated lean -- a real ruling, not a rubber-stamp); COS
per-DC-only confirmed; mirror sync topology independent-per-DC confirmed.

All 11 decisions flipped PROPOSED -> ADOPTED in docs/design-decisions.md.
D-102's body is preserved under a MERGED-INTO-D-101 status line per this
repo's append-only discipline, not deleted. D-101 itself amended: the
metal-admin ULA ruling folded into its family matrix, D-102's tenant/MTU
content folded in as a new section. docs/dc-dc-buildout-design.md Section
10 rewritten from an open list to a ruling record; the stray "Section
D-102" cross-reference corrected to D-101.

Verified, not just asserted: ledger-scan.sh's PROPOSED/OPEN list no longer
contains any of D-100..D-110 -- only D-068/D-071 remain, pre-existing and
unrelated to this gate. Stage 0 of docs/dc-dc-deployment-workflow.md is
CLEARED; workflow doc + visual tracker updated to match.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01QrcJx8TUar7pYAvpGJw57A