Every early return from a write-tool handler skipped both the tool's own
LogCall and transport.go's gated LogCall (which only fires for reads), so a
blocked mutation attempt left no audit trail. registerSDKTool now routes
every write-tool error through LogDenied (fan-out and tag-scope refusals,
by gate name) or LogFailure (everything else), keeping the successful-write
path logging its own resolved server count exactly as before.
Also close a live scope gap surfaced while reviewing this: POST
/api/keys/:id/assign called services.AssignKey with an unscoped GetServer
lookup, so a tag-restricted token could assign a key to a server outside
its restriction. The handler now resolves the target through
GetServerScoped first, matching its sibling revoke route, and the route is
recorded in serverScopedRoutes.