refactor: enforce features/ structure for all library packages - #263

In
`@packages/riviere-builder/src/platform/domain/collection-utils/deduplicate.spec.ts`:
- Line 2: The test file deduplicate.spec.ts under the platform domain layer
imports and tests the features-layer function deduplicateStateTransitions; move
that test file so it sits next to the implementation of
deduplicateStateTransitions in the features building/domain/enrichment tests,
update the import to a local relative import (remove cross-layer import), and
run tests to ensure no remaining platform→features test dependency remains.

In `@packages/riviere-extract-ts/src/index.ts`:
- Around line 15-33: The public barrel currently exports the 11 internal rule
functions (evaluateLiteralRule, evaluateFromClassNameRule,
evaluateFromMethodNameRule, evaluateFromFilePathRule, evaluateFromPropertyRule,
evaluateFromDecoratorArgRule, evaluateFromDecoratorNameRule,
evaluateFromGenericArgRule, evaluateFromMethodSignatureRule,
evaluateFromConstructorParamsRule, evaluateFromParameterTypeRule); remove these
from the public export list in packages/riviere-extract-ts/src/index.ts and
either re-export them from an internal testing path (e.g., ./internal or
./testing) or keep them as non-exported/private functions inside
./features/extraction/domain/value-extraction; update any unit tests to import
from the new internal path if needed and ensure public API continues to export
only applyTransforms, ExtractionError, ExtractionContext/Result types,
ParameterInfo, and MethodSignature so consumers use
ExtractionConfig/extractComponents only.

In
`@packages/riviere-builder/src/features/building/domain/enrichment/deduplicate-transitions.spec.ts`:
- Around line 49-92: Add a test that covers the reverse trigger-asymmetry: call
deduplicateStateTransitions with an existing transition that includes trigger:
'submit' and an incoming transition without a trigger (both with same from/to)
and assert the incoming one is treated as non-duplicate (i.e., result contains
the incoming transition or the expected retained transition). Locate the test
suite around deduplicate-transitions.spec.ts where other trigger-asymmetry cases
are defined and mirror the structure of the existing "treats different triggers
as non-duplicates" test but swap which side has the trigger.

In
`@packages/riviere-extract-ts/src/features/extraction/domain/value-extraction/index.ts`:
- Around line 8-10: The exports here use fragile deep-relative imports for
applyTransforms and ExtractionError (from '../../../../platform/...'); replace
them with a stable import surface—either add a barrel file in platform/domain
(exporting string-transforms/transforms and ast-literals/literal-detection) and
re-export from that barrel, or configure a TypeScript path alias (e.g.,
`@platform/domain/`*) and update the exports to import applyTransforms and
ExtractionError from the new stable path; update the export statements in
index.ts to reference the barrel or alias so cross-boundary moves won't break.