v6.4.0: Browser/Edge Read Path

[flyingrobots]

Outcome

Browser and edge read paths are designed and proven enough to know which runtime boundaries are real, which adapters are missing, and what compatibility contract git-cas can honestly claim.

Scope

• Inventory Node-specific read-path assumptions.
• Design browser/edge adapter boundaries.
• Prove at least one focused runtime portability slice before expanding scope.

Required Proof

• Design cycle before implementation.
• Runtime or adapter tests that exercise the actual portability surface.