Move chunks into the canonical source model

docs/internal/modules.md

@@ -57,7 +57,8 @@ rules are defined in the
 The generic chunker validates the source document, walks units in configured
 windows, clones each selected unit, and emits deterministic ordered chunk IDs.
 Overlap changes the next window start but never reorders units. It records the
-first and last unit and unit count in chunk metadata.
+first and last unit and unit count in chunk metadata, and derives the chunk's
+canonical source reference from those unit references.
 
 The accepted options and defaults are defined in
 [Configuration](../config.md#implemented-production-modules). Generic
@@ -68,7 +69,7 @@ framework validation canonicalizes the returned unit slices before extraction.
 The scene chunker prepares a structured Scriptorium request from the full
 transcript, session, and optional D&D reference inputs. It validates the model's
 scene boundaries against source-unit IDs and converts them into deterministic
-chunks.
+chunks with canonical source references spanning each scene's units.
 
 Scene validation requires sequential, contiguous, non-overlapping coverage from
 the first source unit through the last. Each chunk contains JSON scene content

docs/internal/overview.md

@@ -31,7 +31,7 @@ a sorted set of artifact lanes before the runner constructs any stage module.
 | `internal/core/artifacts` | Run-manifest and provenance models. |
 | `internal/core/config` | Defaults, YAML parsing, environment overrides, validation, redaction, and effective pipeline resolution. |
 | `internal/core/diagnostics` | Scoped run directories, diagnostics writers, atomic writes, and retention decisions. |
-| `internal/core/source` | Generic source documents, units, references, lookup, and validation. |
+| `internal/core/source` | Generic source documents, units, chunks, canonical references, lookup, validation, and deterministic source digests. |
 | `internal/core/workspace` | Effective workspace settings, confined paths and writes, checkpoint identity, and checkpoint manifest models. |
 
 ## Framework Packages

docs/internal/pipeline.md

@@ -77,7 +77,8 @@ normalize requests retain access to the original source material.
 Source validation requires every unit to carry a canonical self-reference to
 its containing document and its own unit ID. Explicit clone, checkpoint, and
 debug boundaries retain that reference, and the canonical source digest covers
-it deterministically.
+it deterministically. Chunks use the same source model and carry one canonical
+reference spanning the first selected unit through the last.
 
 `pipeline.RunOutput` carries the run manifest, accepted normalized results,
 rejected results, warnings, checkpoint events, and logical files returned by the
@@ -115,13 +116,15 @@ whose results are accepted and used.
 ## Chunk Canonicalization
 
 Before lane execution, generic validation requires unique chunk IDs, matching
-source identity, indexes matching returned order, valid ordered boundaries,
+source identity, indexes matching returned order, a valid canonical reference,
 non-empty content and media type, and at least one valid source unit per chunk.
-Units may not repeat inside a chunk and must preserve source-document order.
+Units may not repeat inside a chunk and must form a contiguous range in
+source-document order. The chunk reference must exactly match the source and
+the first and last unit references.
 
 The runner then rebuilds each chunk's unit slice from the source document by
-unit ID. It preserves the module-owned boundaries, content, media type, and
-cloned metadata. The framework permits gaps and overlap between separate
+unit ID. It preserves the canonical reference, content, media type, and cloned
+metadata. The framework permits gaps and overlap between separate
 chunks; stricter coverage policy belongs to the chunk implementation.
 
 ## Validation And Retries