Self / Children / Parent accessors with sync-indexer + async-method
shape. Flattening pipeline emits ScriptScope per resolved script;
ScriptCompilationService seeds the accessors at execution time with
no new actor messages or lookup paths.
Phased: (1) runtime accessors + Scope on ResolvedScript, (2)
flattening + deploy round-trip, (3) editor metadata fetch for child
+ parent shapes, (4) Monaco completion / hover / diagnostics
(SCADA006 unknown attribute, SCADA007 unknown composition).
Out of scope: per-template Roslyn-generated typed accessors,
locking-aware writes (covered by lock-enforcement pass), and
sibling-of-sibling chained navigation.
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