Add deterministic incremental adapter assembly

docs/INCREMENTAL_INDEXING.md

@@ -64,6 +64,25 @@ Each `AdapterSourceProjection` owns:
 Ownership must be deterministic. Two sources may not produce the same primary node or the same
 function logic projection.
 
+Some language tools emit overlapping raw evidence before ownership can be resolved. An incremental
+loader may additionally implement:
+
+```python
+def assemble_projection(
+    manifest: AdapterManifest,
+    contributions: tuple[AdapterSourceProjection, ...],
+) -> AdapterAssembly: ...
+```
+
+DocForge caches and invalidates the source contributions normally, then passes the complete current
+contribution set to this pure assembly step. The assembler must deterministically select or merge
+overlapping evidence and return one valid final graph and Logic set. It may not read hidden source
+state or create a second extraction cache. The final identity, revision, and source hash must match
+the manifest exactly.
+
+Without an assembler, the stricter default remains in force: two contributions may not publish the
+same primary node or Logic owner.
+
 ## Invalidation
 
 DocForge invalidates a source when:

docs/PROJECT_ONBOARDING.md

@@ -123,6 +123,7 @@ All frontends emit the same DocForge contracts:
 - `AdapterManifest` inventories fingerprinted extraction units and dependencies.
 - `AdapterSourceProjection` owns nodes, relationships, and optional function Logic for one unit.
 - `AdapterProjection` provides the deterministic complete rebuild.
+- `AdapterAssembly` optionally resolves overlapping raw evidence into the single published graph.
 
 Language metadata may differ. Graph publication, indexing, querying, visualization, and MCP
 behavior do not.
@@ -130,6 +131,11 @@ behavior do not.
 Done when repeated extraction produces the same stable identities without inferred or guessed
 facts.
 
+When compiler or language tooling repeats shared declarations across extraction units, use the
+optional assembly contract. Cache the raw source contributions through DocForge, then
+deterministically select or merge ownership from the complete contribution set. Do not hide a
+second extraction cache inside the project adapter.
+
 ### 5. Build-system evidence
 
 #### C and C++