Write workspace checkpoints during runs

docs/internal/overview.md

@@ -42,9 +42,11 @@ production modules.
 - `internal/framework/contracts`: interfaces and request/result structs for
   input adapters, chunkers, extractors, mergers, normalizers, validators, output
   encoders, and structured LLM clients.
+- `internal/framework/checkpoint`: workspace-backed checkpoint recorder and
+  checkpoint payload envelope serialization.
 - `internal/framework/pipeline`: module registries, module specs, profile
-  resolution, capability checks, run orchestration, warnings, validation, and
-  manifest population.
+  resolution, capability checks, run orchestration, checkpoint recorder
+  boundaries, warnings, validation, and manifest population.
 - `internal/framework/llm`: Scriptorium-backed structured-output client,
   prompt/schema asset registry, scheduler, schema registry, and secret
   redaction.

docs/internal/pipeline.md

@@ -71,6 +71,12 @@ to chunk, extract, merge, and normalize requests; LLM-backed modules forward it
 through their structured completion requests so Scriptorium can include it in
 prompt execution metadata.
 
+When workspace resume checkpointing is enabled, the CLI constructs a checkpoint
+recorder after pipeline resolution and reference materialization and passes it
+through `pipeline.RunInput`. The runner records source, chunk, extract, merge,
+and normalize outcomes through that interface. Concrete modules do not receive
+workspace paths and do not write checkpoint files directly.
+
 ## Registries And Module Specs
 
 `pipeline.Registries` holds concrete constructors for execution. A