fix(build): repair postprocessor, generate full artifacts, untrack lib output

The build:postprocess sed matched only the generator's old single-line
`var global = Function('return this')();`. The current protoc-gen-js emits a
multi-line IIFE whose last resort is that same call, so the pattern silently
stopped matching and the dynamic-function fallback shipped in published
bindings -- it was present in all 12 generated files. Building a function from
a string is blocked under strict CSP, which is where these bindings run.

Replace the one-liner with tools/postprocess-lib.js, which rewrites the call
itself rather than the surrounding block (covering both the legacy and current
shapes) and then fails the build if any dynamic-function fallback survives.
This also drops the `sed -i ''` invocation, which is BSD-only and fails on the
GNU sed in CI and on Linux developer machines.

prepare ran only build:js, so Git-based installs got JavaScript but no
lib/proto.json -- that is produced by build:json and is present in published
packages. Point prepare at the full build so both artifact sets exist.

lib/ is gitignored generated output, but lib/messages-ripple_pb.js and its
.d.ts were committed, creating a second stale-prone source of truth. Untrack
both; they are regenerated by the build. lib/.keep stays.

Author: pastaghost