Publishing adapters

Today: adapters ship built-in with Parallax.

Planned distribution:

.parallax/adapters/          project-local
~/.parallax/adapters/        user-installed
package registries           versioned adapter crates / packs

Lockfiles

parallax.lock pins adapter versions for reproducible migrations.

plx analyze . --write-lock
plx adapters update --check

Breaking mapping changes between adapter versions must surface as review-required diagnostics (not silent semantic drift).