Accept direct source lookup on results

docs/roadmap/api.md

@@ -4,9 +4,9 @@ Status: decisions accepted; implementation has not begun.
 Baseline: `a050986` and the revision-pinned [API review](review.md).
 
 This document records the accepted cleanup from that review. The goal is clearer
-public vocabulary and recording methods before v1.0.0, preserving existing
+public vocabulary, recording methods, and direct source lookup before v1.0.0,
-behavior. The review remains the catalog and analysis; its other assessments
+preserving existing behavior. The review remains the catalog and analysis; its
-are not automatically adopted by these decisions.
+other assessments are not automatically adopted by these decisions.
 
 ## Accepted Changes
 
@@ -20,6 +20,7 @@ are not automatically adopted by these decisions.
 | D6 | Replace `Resolution.Record` with the two intent-specific methods below. Retain `ChangeKind` and its inspection constants. |
 | D7 | Rename `LoadSecretsDir` to `LoadSecretsIntoEnvironment`, making process-environment mutation explicit. Preserve its signature apart from the name, report-plus-error behavior, and existing bootstrap semantics. |
 | D8 | Remove `CodeOptionsUnavailable` after confirming there is no intentional supported role. Do not introduce a failure merely to give the code a producer; a concrete reason to retain it should be brought back for discussion. |
+| A1 | Add `Result.Source(id)` for direct lookup of acquired-source evidence, alongside ordered `Sources()` enumeration and passive `SourceContext(id)` resource access. |
 
 ### Recording Methods (D6)
 
@@ -53,14 +54,27 @@ Document the modes together, preserving these distinctions:
   invocation or acceptance. Preserve nil-versus-observed-absence meaning,
   explicit null, locations, consumption, and redaction. No acceptance flag is added.
 
+### Direct Source Lookup (A1)
+
+```go
+func (r *Result[T]) Source(id string) (SourceInfo, bool)
+```
+
+Look up an acquired source by its load-local ID, returning the same information
+represented in `Sources()` as a detached record. Empty or unknown IDs return
+false. The query performs no source acquisition, filesystem access, or credential
+lookup. Reuse existing source lookup and conversion machinery where practical;
+no public registry, indexing strategy, or constant-time guarantee is required.
+
 ## Scope And Follow-Up
 
 Implement the selected changes with corresponding declaration comments, owning
 documentation, examples, tests, and affected consumer call sites. Preserve the
 existing loading, composition, presence, inspection, ownership, and diagnostic
-contracts except for the expressly selected API replacements/removals above.
+contracts except for the expressly selected API replacements/removals and addition
+above.
 This record does not authorize release publication or a broader API redesign.
 
-A1 (`Result.Source(id)`) and A2 (public path comparison) are not selected for this
+A2 (public path comparison) is deferred. It can be considered separately as a
-cleanup. Both can be considered separately as compatible additions; path
+compatible addition once a concrete use case and an explicit equality definition
-comparison needs a concrete use case and an explicit equality definition.
+are established.