Reject unsupported WebApp identity and align family guidance

Reject explicit NFC settings before WebApp services start and when settings
are loaded or saved. Preserve Legacy interoperability, and clarify host
support and the Commonlib-first publication prerequisite.

docs/design_docs/tweak_compatibility.md

@@ -34,10 +34,15 @@ admission checks and supported transports.
 
 The central replication gate, mismatch dialogues, and RedFlag Fetch preparation
 consume the same effective differences. The P2P transport retains its separate
-policy: ordinary representation differences warn without rejecting transfer,
-while its existing passphrase and peer checks still apply. NFC path identity
-is outside that warning-only policy: P2P refuses version `1`. Sharing assessment
-does not make the central replication policy appropriate for every transport.
+policy: ordinary representation and case differences warn without rejecting
+transfer, while its existing passphrase and peer checks still apply. Path
+identity has a separate required check: both peers must use the same version,
+and a version mismatch rejects before replication. Commonlib `0.3.0` includes
+NFC protocol support for Journal and P2P, but the matching CLI and Obsidian host
+adoption remains an unreleased extension tracked by
+[the Unicode path identity design](unicode_path_identity.md). Sharing
+assessment does not make the central replication policy appropriate for every
+transport.
 
 ## Host responsibilities
 
@@ -96,7 +101,8 @@ failed transfer into a completed transfer.
 ## Verification boundaries
 
 Commonlib tests protect missing-value interpretation, representation differences,
-directional consequences, immutable results, central admission, and P2P policy.
+directional consequences, immutable results, central admission, and P2P policy,
+including the distinction between ordinary warnings and a path-version mismatch.
 LiveSync unit tests protect ordinary versus reconstruction choices, trial-setting
 selection, partial-setting adoption, and invalidated decisions. RedFlag tests
 protect the distinction between adopting settings for Fetch and retaining local