Prepare canonical party and derived players inputs

docs/internal/stage-prepare.md

@@ -39,6 +39,9 @@ Materialize canonical current-session inputs before processing stages.
 - materializes a configured spell catalog with checksum and provenance, or
   safely removes an obsolete canonical spell catalog and its manifest record
   when the effective input is omitted.
+- in canonical party mode, copies the validated raw party bytes unchanged and
+  deterministically generates the prepared players projection; legacy mode
+  continues to copy its opaque party and explicit players sources.
 - scans enabled configured artifact inputs for `narratio.previous_session.artifact.*` requirements.
 - clears managed `previous/` state on every invocation, then, when requirements exist:
   - resolves the pointer-selected previous source through the shared resolver;
@@ -62,7 +65,8 @@ mapping, while the isolated legacy reader rejects ambiguous fallback matches.
 Prepare records a versioned semantic-configuration fingerprint for the
 resolved campaign/session selection, local-versus-S3 audio mode and canonical
 audio names, stable-input ownership/presence, previous-session identity, and
-the effective previous-artifact requirement set. A change reruns prepare and
+the party mode plus canonical players projection version, and the effective
+previous-artifact requirement set. A change reruns prepare and
 stales its fixed descendants. Existing successful records without this
 evidence rerun once when selected.