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LDC-E8101 — Construct above the declared layer

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# LDC-E8101 — Construct above the declared layer

## What it means

A package can declare a layer ceiling, and every construct in it must fit
under that ceiling. The layer of a program is inferred from the constructs
it actually uses: plain computation stays at the bottom, defaults and
exceptions sit one step up, and conflict consumption — reasoning that reads
the support status of a claim — belongs to the top layer. When the
inference rises above the declared ceiling, the compiler stops at the
construct that raised it and names the lowest layer that would accept it.

The ceiling is one-sided: declaring a higher layer than the program needs
is never an error. Either raise the declared ceiling to the named layer or
rewrite the construct so it stays within the declared one.

## Example

```run
{"argv": ["check", "$ROOT/example.law", "--layer", "L0"], "files": {"example.law": "language \"law.core\" version \"0.2\";\npackage probe.layer version \"0.1.0\";\nnamespace \"urn:law:probe:layer\";\n\nrelation disputed(subject: Text) kind institutional;\n\nrelation contested(subject: Text) kind institutional;\n\nrule Contested strict {\n    for v0: Text;\n    when supported(disputed(v0));\n    then contested(v0);\n}\n"}, "expect": "LDC-E8101"}
```

## Fix

```run
{"argv": ["check", "$ROOT/example.law", "--layer", "L3"], "files": {"example.law": "language \"law.core\" version \"0.2\";\npackage probe.layer version \"0.1.0\";\nnamespace \"urn:law:probe:layer\";\n\nrelation disputed(subject: Text) kind institutional;\n\nrelation contested(subject: Text) kind institutional;\n\nrule Contested strict {\n    for v0: Text;\n    when supported(disputed(v0));\n    then contested(v0);\n}\n"}, "expect": null}
```

## Engine message

The engine reports this in its own wording:

```text
$ROOT/example.law:11:10: error LDC-E8101: conflict consumption `supported` requires layer L3 (contentious — dispute), but the package declares L0: raise `semantic_layer` or rewrite the construct within the layer
```

## Related

- [LDC-E8102](/diagnostics/LDC-E8102/) — the neighbouring layer refusal.