[L4-PORT-DES] Serial design: owning ports + forbidden dual writers for projected types

[jason931225]

Lane L4-PORT-DES (phase P4).
Objective: Serial design: owning ports + forbidden dual writers for projected types
depends_on: ['L3-ONT-CELL', 'L2-APR']
tip_serial: False
hold_touch: prepare-only:H2
Success: admit green + PR or stacked commit; path-disjoint allowlist; must_read first.
Transport: .grok/bin/mm-role → codex exec / claude -p.
Forbidden: docs/current/** edits as authority; multi-tip; Grok model: sol/claude; HOLD clearance by implication.