Align discovery ownership and contributor documentation

docs/internal/overview.md

@@ -7,10 +7,13 @@ private state; public signatures and fields do not expose engine types.
 
 Implemented component owners:
 
-- `internal/engine` owns host and native-filesystem source acquisition,
-  grouped strict composition, recursive precedence assembly, per-input mapping
-  and sequence-item placement, YAML collection declarations and operations for
-  identified sequences, and application identity registrations for strict
+- `internal/engine` owns host and native-filesystem source acquisition and
+  explicitly selected configuration discovery. A search resolves once during
+  shared acquisition; the selected concrete file or absent-input state then
+  follows the existing composition, metadata, and resource-context lifecycle.
+  It also owns grouped strict composition, recursive precedence assembly,
+  per-input mapping and sequence-item placement, YAML collection declarations
+  and operations for identified sequences, and application identity registrations for strict
   composition, inheritance, and final validation. It applies the selected
   collection operation at precedence boundaries and owns dependency-ready,
   destination-local inheritance before typed decoding. CLI assignment follows
@@ -31,9 +34,9 @@ Implemented component owners:
   or records. Callback wrappers pass only live engine context during a callback;
   `Result.Config` is detached and its private inspection remains frozen
   independently.
-- Root conversion files explicitly cross the path, record, callback, secret, and
-  error boundaries. There are no public aliases, anonymous engine embeddings, or
-  public engine bridge methods.
+- Root conversion files explicitly cross the path, record, callback, secret,
+  search-description, and error boundaries. There are no public aliases,
+  anonymous engine embeddings, or public engine bridge methods.
 - Root `Diff` and `Difference` provide the public comparison boundary and
   convert detached engine records to root-owned paths and snapshots; consumer
   examples own presentation of the safe changed regions.
@@ -53,7 +56,9 @@ these constraints and rejects exported aliases, fields, or signatures involving
 internal types.
 
 The [configuration contract](../config.md) owns implemented YAML and lifecycle
-semantics, including [input destinations](../config.md#input-destinations),
+semantics, including
+[configuration discovery](../config.md#configuration-discovery),
+[input destinations](../config.md#input-destinations),
 [shared source-version checks](../config.md#shared-source-version-checks), and
 [effective configuration diffs](../config.md#effective-configuration-diffs).
 The [strict composition contract](../config.md#strict-document-composition)
@@ -78,5 +83,7 @@ records the shared dependency-ready ordering decision; [ADR
 0016](../adr/0016-independent-import-controls.md) records the independent
 selection controls. [ADR 0017](../adr/0017-collection-sequence-policy.md) and
 [ADR 0018](../adr/0018-cli-after-structural-resolution.md) record collection
-operations and CLI ordering. The [import internals](imports.md) document candidate and
-namespace identities, discovery and scheduling, and the bounded algorithms.
+operations and CLI ordering. [ADR 0019](../adr/0019-explicit-configuration-discovery.md)
+records explicit main-file discovery. The [import internals](imports.md)
+document candidate and namespace identities, discovery and scheduling, and the
+bounded algorithms.