Lift the Phase-4-lite restrictions now that import resolution is lexical:
- `create_group_script` (group_scripts_api): allow `kind = module` and
group scripts with `import`s; record the import edges. Module-shape and
sandbox-ceiling validation stay.
- The declarative apply path already reconciles group modules generically
(`BundleScript.kind` + `owner.script_owner()` flow through
`reconcile_node_tx`); no change needed beyond stale-comment fixes.
Adds the §5.5 dangling-import plan check (single-node plan/apply):
`check_imports_resolve` rejects an `import "<m>"` that resolves to neither a
bundle-local module nor a module reachable lexically up the node's chain —
caught at plan time instead of as a runtime 404. Roots resolution at the
node's owner (an app node reaches ancestor group modules; a group node walks
its own ancestry). ApplyService gains an injected `ModuleSource`. The tree
path opts out (a node may import a module created by another node in the same
uncommitted tx); the runtime check is the backstop there.
Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
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