fix(update): wire up the bare-keyword mirrors mode

`update lock`, `update nothing`, and `update mirrors` were treated as
ordinary full updates: the resolver picked the highest matching
version of every root require and the install step rewrote refs from
the repository, masquerading transport metadata refreshes as content
changes (and accepting brand-new root requires the lock had never
seen). Mirror Composer's `setUpdateMirrors(true)` flow:

- Detect the bare-keyword form and skip composer.json's require /
  require-dev entirely; require each locked package by exact version
  instead. This drops fresh root requires Mozart shouldn't yet honor
  and pins existing ones to their lock version.
- After lockfile generation, walk each new entry and copy the OLD
  lock's source/dist reference back when the source/dist *type*
  matches, mirroring `LockTransaction::updateMirrorAndUrls`. URL and
  mirrors update; ref stays put — so a repo rename or mirror flip
  emits no Update operation, but a real type change (`hg` → `git`)
  still does.

1 files changed, 2 insertions, 2 deletions

diff --git a/crates/mozart/tests/installer.rs b/crates/mozart/tests/installer.rs
index 189a7c9..f304b72 100644
--- a/crates/mozart/tests/installer.rs
+++ b/crates/mozart/tests/installer.rs
@@ -388,8 +388,8 @@ installer_fixture!(update_installed_alias);
 installer_fixture!(update_installed_alias_dry_run);
 installer_fixture!(update_installed_reference);
 installer_fixture!(update_installed_reference_dry_run);
-installer_fixture!(update_mirrors_changes_url, ignore);
-installer_fixture!(update_mirrors_fails_with_new_req, ignore);
+installer_fixture!(update_mirrors_changes_url);
+installer_fixture!(update_mirrors_fails_with_new_req);
 installer_fixture!(update_no_dev_still_resolves_dev);
 installer_fixture!(update_no_install);
 installer_fixture!(update_package_present_in_lock_but_not_at_all_in_remote);