Finalize previous-session artifact documentation and restore-analyze continuity coverage

docs/internal/stage-archive.md

@@ -1,17 +1,19 @@
 # Stage: archive
 
 ## Purpose
-Publish run records and promoted session artifacts to object storage, then atomically advance the remote current pointer.
+Publish durable run/session state to object storage, then atomically advance remote current state.
 
 ## Inputs and Outputs
 Inputs:
 - session manifest and prerequisite stage records
 - run root contents under `runs/{run_id}/`
 - promotion rules with artifact `source` IDs and archive `dest` paths (`archive.promote_artifacts`)
+- session-level `previous/**` cache files when present
 
 Outputs:
 - uploaded run files under `{session_prefix}/runs/{run_id}/...`
 - uploaded promoted artifacts under `{session_prefix}/...`
+- uploaded session previous-cache files under `{session_prefix}/previous/...` when present
 - `{session_prefix}/current/manifest.json`
 - `{session_prefix}/current/run_id.txt` written last
 
@@ -21,6 +23,7 @@ Owns:
 - Prerequisite stage success enforcement
 - Run file collection and upload (excluding `audio/`)
 - Promotion rule resolution and upload
+- Session previous-cache file collection/upload
 - Commit pointer publish order
 
 Does not own:
@@ -43,8 +46,10 @@ Does not own:
 ## State and Manifest Behavior
 - Requires `prepare`, `transcribe`, `merge`, `polish`, `normalize`, `trim`, and `analyze` status `succeeded`.
 - Resolves bucket/prefix from manifest identity first, then config fallback.
+- Uploads session `previous/**` files as durable session state when the local `previous/` directory exists.
 - Writes metadata including:
   - upload counts/paths
+  - `previous_files_uploaded` and `previous_uploaded_paths`
   - `current_manifest_key`
   - `current_run_id_key`
   - `current_pointer_written`
@@ -64,5 +69,6 @@ Does not own:
 
 ## Architectural Invariants
 - Run upload excludes `audio/` subtree.
+- Session `previous/**` is archiveable durable input/provenance state, not run-local output.
 - `current/manifest.json` uploads before `current/run_id.txt`.
 - `current/run_id.txt` is the remote publish commit marker.