corpus: message-literal list elements in 10_literal_args + carrier golden (#176)

[trendvidia]

Closes #176.

Pairs the corpus with trendvidia/protocompile#127 → trendvidia/protocompile#128 (merged post-v0.21.0): the reference parser now accepts message literals as list elements at annotation arguments, so the corpus pins the shape.

What changed

• 10_literal_args.proto — new annotation samples(values: any) + a fourth Order field using @samples([Money{currency: "USD", units: 5}, Money{currency: "EUR", units: 7}]). The unused protowire/schema/v1/annotations.proto import is dropped (the incidental hygiene note in Corpus: message-literal list elements in 10_literal_args + 11 carrier golden (RFC-001 §8.1 LiteralValue.literal) #176 — the fixture only uses locally-declared annotations).
• 11_literal_carrier_golden.textproto — pins the lowered list-of-message shape: each element is LiteralValue.literal wrapping Literal.message, its own google.protobuf.Any serialized at lowering (EUR/7 wire bytes \n\003EUR\020\007). While re-authoring, the golden is realigned to the actual reference-lowered carrier (verified by compiling the fixture with pxf build on the bumped fork and dumping ext 50401): the fixture writes every argument positionally, so AnnotationArg.name is empty per §8.1's "empty for positional", and location.file is the fixture's import path 10_literal_args.proto rather than the old notional fixtures/literals.proto. The previous name: "value"/notional-path entries predated the toolchain (authored at spec: finalize Literal carrier shape (RFC-001 §8.1) #99/spec: pin message-literal source grammar (RFC-001 §5.1) #108).
• invalid/untyped_list_element.proto — MUST-NOT-COMPILE fixture for the untyped form [{...}] under an any-typed parameter (RFC-001 §5.1 literal rule 1), plus its manifest row. Rejected with exactly protocompile's documented diagnostic: message-literal list element in argument "values" ... requires an explicit type name.
• go.mod — fork bump v0.20.0 → v0.21.1-0.20260725214716-467a41569c93 (the CI: no build coverage for editors/ — vscode and jetbrains changes merge unverified #128 merge commit; includes v0.21.0). Consequences picked up:
  • checkKnownGaps entry for reserved_sensitive_class.proto removed — protocompile#123 closed in v0.21.0 and TestCheckInvalidFixtures now asserts genuine rejection (no skip).
  • Stale protocompile#121 drift note in 14_refinement_kinds.proto updated (fixed in v0.21.0).

internal/schemaext (nested test-only module) stays on v0.20.0 — its harness compiles fixtures 01–06 only and is untouched by this change.

Verification

• go test ./... clean on the bumped fork.
• Golden authored from actual lowered output (not hand-derived): pxf build over the fixture, carrier dumped via pwsv1.E_FieldAnnotations and diffed against the golden.
• pxf build --check invalid/untyped_list_element.proto fails with the expected explicit-type-name diagnostic.

Downstream

Un-blocks revisiting the @http responses parameter deferral — tracked in #177.

Precedent: trendvidia/protocompile#121/#123/#127 corpus/toolchain pairing.