nex-pkg 0.25.9

Package manager UX for nix-darwin + homebrew
Documentation
## 1. Registry read/search/info
<!-- specs: armory/registry -->

- [x] Add registry config shape to local Nex config.
- [x] Add Armory index fetch/parse support.
- [x] Extend `nex search` to include Armory registry entries.
- [x] Add `nex info <kind>/<id>` for Armory metadata and dependencies.
- [x] Validate with unit tests and existing command checks.

## 2. Lock-only graph resolution
<!-- specs: armory/lock -->

- [x] Add package lock structs and JSON serialization.
- [x] Add state path helpers for `~/.local/state/nex/packages.lock.json` and activation lock.
- [x] Implement dependency graph resolver over fetched registry indexes.
- [x] Detect missing required dependencies.
- [x] Detect dependency cycles and report the cycle path.
- [x] Collapse duplicate refs and reject conflicting version/digest records.
- [x] Route `nex install <kind>/<id>` to Armory lock-only install while preserving existing Nix/Homebrew install behavior for bare package names.
- [x] Implement `--dry-run` output for Armory installs.
- [x] Write package lock for non-dry-run installs.
- [x] Write provisional Omegon activation lock for Omegon-runtime roots.
- [x] Add tests for graph resolution, cycle detection, lock serialization, and install routing.

## 3. OCI fetch, store, and validation
<!-- specs: armory/store -->

- [x] Add content-addressed Nex package store layout.
- [x] Add OCI fetch abstraction, initially shelling out to `oras` when available.
- [x] Verify fetched payload digest against registry metadata by computing local SHA-256 after fetch.
- [x] Enforce registry trust policy, failing closed for signed registries without verifiable metadata.
- [x] Extract payloads into the Nex store.
- [x] Invoke existing validators for `machine-profile` and `materialization-payload`; fail closed for `forge-template` until schema validation exists.
- [x] Update package lock entries with installed paths and verification status.
- [x] Rewrite Omegon activation lock with installed local paths after materialization.
- [x] Add tests for digest mismatch, missing `oras`, validator dispatch, store path calculation, and lock state updates.

## 4. Omegon activation handoff
<!-- specs: armory/activation -->

- [x] Finalize activation lock schema.
- [x] Populate activation lock entries with local package paths after store materialization.
- [x] Encode runtime defaults for `profile`, `agent`, `extension`, and `workstation` roots.
- [x] Add `nex lock refresh` to re-resolve roots and update locks.
- [x] Add `nex lock status` to inspect roots, package state, digests, and local paths.
- [x] Add remove/list UX for installed Armory package roots.
- [x] Add tests proving Omegon-runtime activation locks do not require registry access.