v2: wire arch:check (safer-architecture-lsp) for the six v2 packages before Phase 3

[chughtapan]

Deferred from #891 / PR #893 (Phase 2 scaffolding).

Problem

Every v1 package exposes an arch:check nx target running
safer-architecture-lsp check .. The six v2 packages expose only build and
lint, because scripts/gen-architecture-configs.mjs writes
safer-architecture.config.json only for packages/*, and
package.json → arch:config:check diffs only packages/*.

Consequence: the deep-module rules in docs/architecture/components.md
("Deep-module design rules" — public interfaces expose capabilities not
mechanisms, one canonical owner per cross-package flow, no pass-through
accessors) have zero mechanical enforcement on v2. Those are precisely the
constraints safer-architecture-lsp checks (maxPublicExports, facadeFiles,
folder child counts, layers).

This was correct to skip while the packages are empty skeletons — an empty
package passes trivially and the config would encode nothing. It stops being
correct the moment real code lands.

Fix recipe

1. Extend scripts/gen-architecture-configs.mjs to emit
   v2/*/safer-architecture.config.json.
2. Widen arch:config:check to diff v2/* as well as packages/*.
3. Add the arch:check nx target to each v2 package.json, matching the v1
   shape.

Timing

Blocking before Phase 3 lands ported simulator code. Cheapest to do while the
packages are still empty.

[chughtapan]

Filed from PR #893 (Phase 2 scaffolding, #891).