feat(resolve): origin through top-level calls + sibling-site scope fixes (slices 2b-3)

[Hessesian]

Stacked on #331 (slices 1-2). Base is that branch; retarget to main once #331 merges.

Slice 2b — top-level calls

• find_fun_return_type_reachable_declared / InferDeps::find_fun_return_type_reachable_with_origin: a bound top-level function's return type reports the file it was written in (the strategy used to assume the caller's file).
• A bound top-level function with no declared type gets its body's type, or Unit (Kotlin only), like a member method. A signature with no = after its parameter list is Unit without parsing the declaring file.

Slice 3 — the same bug at sibling sites

• value_path_anchor resolved a field's type name from the caller's file; it was written in the field's declaring file.
• references_verify started the supertype walk from the call site for a Reference candidate, a file that declares nothing of the receiver's type, so a genuine subtype reference was rejected as Unrelated. It now starts from the receiver type's declaring file; unresolvable → kept, never rejected.
• resolve_receiver_callee_in_type_scope splits the type scope from the caller (extension scope stays the caller's); used by find-references' arity query.

Regressions found and fixed while measuring (each with a red test)

• A declared return type cut off from the 120-char indexed detail (multi-line parameter list) was mistaken for "no type declared" and answered Unit (Moneta safeFlow → startScoring().collectEmit). The full collected signature is now read first.
• The Unit/body rule leaked to Java methods (FormatUtil.formatAmount → Unit, 400+ bogus typed receivers). It is now Kotlin-only.

Tests (red before)

top_level_call_member_resolves_in_the_file_the_return_type_was_written_in, top_level_expression_body_call_member_resolves_through_the_inferred_return, value_path_field_type_is_resolved_in_the_fields_declaring_file, subtype_call_site_in_a_file_that_declares_neither_type_is_kept, receiver_callee_resolves_the_receiver_type_name_in_its_own_scope, top_level_return_type_declared_after_a_multi_line_parameter_list_is_not_unit, undeclared_return_inference_never_applies_to_a_java_method, signature_declares_an_expression_body_only_for_an_equals_after_the_parameter_list.
cargo test (2049), clippy -D warnings, fmt clean.

Moneta (resolution-accuracy Moneta/android)

	main	#331 (slices 1-2)	this stack
member recall	92.1%	93.0%	93.0%
member CstResolved	192,257	194,405	195,802
member Gap	8,653	7,382	7,267
FilteredCandidate	7,905	7,341	7,437

Run-to-run noise on identical code is about ±0.3pp / ±400 FilteredCandidate (JAR promotion budget).

🤖 Generated with Claude Code

[Copilot]

Copilot review overview

🟡 Changes recommended

Inferred body origins are still lost, and truncated long signatures can be incorrectly classified as returning Unit.

Review effort: Balanced
Findings: 2

Open (2)

• Inferred return types lose their declaration origin · New
• Truncated signatures are incorrectly classified as Unit · New

What changed in this PR

Extends type-origin tracking through top-level calls and fixes receiver scope selection in resolution and reference verification.

Changes:

• Preserves declaring-file origins for top-level return types.
• Resolves field and receiver types in their declaration scope.
• Adds regression coverage for Kotlin/Java inference and subtype references.

File	Description
src/​indexer.rs	Implements origin-aware return lookup.
src/​indexer/​infer/​chain.rs	Propagates top-level return origins.
src/​indexer/​infer/​deps.rs	Adds origin-aware inference API.
src/​indexer/​infer/​cst_symbol_tests.rs	Tests top-level call resolution.
src/​features/​references.rs	Uses receiver type scope for arity lookup.
src/​features/​references_verify.rs	Anchors hierarchy checks to receiver declarations.
src/​resolver/​extension.rs	Separates type and extension scopes.
src/​resolver/​infer.rs	Infers undeclared Kotlin returns and origins.
src/​resolver/​infer_tests.rs	Tests signature and Java behavior.
src/​resolver/​mod.rs	Exports the scoped receiver resolver.
src/​resolver/​qualified.rs	Resolves field types from declaring files.
src/​resolver/​tests.rs	Tests field and receiver scope fixes.

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