Document chunk plan caching and provenance

docs/internal/diagnostics.md

@@ -22,10 +22,18 @@ constructor.
 
 Typed methods on `RunDirectory` write invocation metadata, redacted effective
 configuration, resolved pipeline/reference data, checkpoint events, source data
-when explicitly requested, manifests, reports, warnings, and error text. The
+when explicitly requested, manifests, reports, warnings, redacted chunk-plan
+summaries, and error text. The
 current filenames and their operator-facing contents are listed in
 [Operations](../operations.md#diagnostics-directory).
 
+The chunk-plan summary records the effective mode, source and candidate
+digests, requested module, lookup decision, materialization action, validation
+decision, and publication decision. Its closed decision values make failures
+and recoverable invalid records inspectable without serializing plan ranges,
+annotations, source content, reference content, prompts, model responses, or
+raw invalid-file bytes.
+
 JSON methods indent their payload and append a newline. All artifact writes use
 a temporary file in the target directory, apply the requested permissions, and
 rename it into place. Artifact resolution accepts only a single relative base
@@ -60,7 +68,8 @@ pipeline results, and the final report. This ordering permits later failures to
 retain the context already established.
 
 Failures before construction have no `RunDirectory`. Later failures write an
-error log, preserve any available partial manifest, and apply a failed-run
+error log, preserve any available partial manifest and chunk-plan summary, and
+apply a failed-run
 retention decision. A diagnostics write failure is itself a command failure so
 the CLI does not report success after losing requested inspection data.