Move project save target planning to app core

docs/modernization/build-inventory.md

@@ -297,6 +297,12 @@ powershell -ExecutionPolicy Bypass -File scripts\automation\apple-remote-build.p
   1024x1024 draw/readback plan counts. It is covered by
   `pano_cli_plan_canvas_document_snapshot_smoke` plus the payload-bearing
   snapshot smoke.
+- `pano_cli plan-canvas-project-save-target` exposes the app-core planner for
+  retained project-save target paths, including the requested PPI path,
+  temporary `.tmp.ppi` path, and timelapse `.pptl` sidecar path. The live
+  `Canvas::project_save_thread` consumes the same planner before retained
+  serialization, and the command is covered by forward-slash, Windows
+  backslash, and invalid-path smokes.
 - Live equirectangular, layer, animation-frame, and cube-face export adapters
   now prepare and log the same payload-bearing canvas document snapshot plus
   shared paint-renderer export-readiness report.
@@ -1174,8 +1180,9 @@ powershell -ExecutionPolicy Bypass -File scripts\automation\apple-remote-build.p
   overwrite prompts, document field updates, title updates, and keyboard/dialog
   cleanup. Existing Save, Save As, Save Version, and save-before-workflow
   prepare and log a payload-bearing canvas document snapshot report, run the
-  app-core pure PPI save-writer route for payload-complete snapshots, and log
-  generated byte counts before delegating to retained `Canvas::project_save`.
+  app-core pure PPI save-writer route for payload-complete snapshots, log
+  generated byte counts, and derive project-save target/tmp/timelapse paths
+  through `pp_app_core` before delegating to retained `Canvas::project_save`.
   Retained legacy UI/canvas
   execution and actual live save serialization remain tracked by `DEBT-0040`,
   `DEBT-0041`, and `DEBT-0042`; the pure snapshot-to-PPI export handoff is

docs/modernization/debt.md

@@ -534,6 +534,13 @@ agent or engineer to remove them without reconstructing context from chat.
   `Canvas::project_save` continues. The retained writer still owns actual save
   serialization, app metadata mutation, progress/threading, and compatibility
   quirks.
+- 2026-06-06: DEBT-0040/DEBT-0042 were narrowed again. `pp_app_core` now owns
+  the retained project-save target path planner for the requested PPI path,
+  temporary `.tmp.ppi` path, and timelapse `.pptl` sidecar path; live
+  `Canvas::project_save_thread` consumes it and
+  `pano_cli plan-canvas-project-save-target` exposes it for automation. Actual
+  PPI serialization, temporary-file swap execution, progress/threading,
+  timelapse sidecar serialization, and app metadata mutation remain retained.
 - 2026-06-05: DEBT-0010/DEBT-0013 were narrowed again. `pp_app_core` now
   exports payload-complete or metadata-only canvas document snapshots through
   the pure `pp_document` PPI writer and rejects snapshots that still require

docs/modernization/roadmap.md

@@ -705,7 +705,11 @@ save-writer route/byte count before retained save continues. The app-core
 snapshot boundary also has a tested pure PPI export helper, and
 `pano_cli plan-canvas-document-snapshot` runs that helper for payload-complete
 snapshots and reports generated byte/dirty-face summaries plus the same
-save-writer route JSON. The same automation now feeds payload-complete snapshots through the shared
+save-writer route JSON. `pp_app_core` also owns the retained project-save target
+path planner for target, temporary PPI, and timelapse sidecar paths; live
+`Canvas::project_save_thread` consumes that planner and
+`pano_cli plan-canvas-project-save-target` exposes it for automation. The same
+automation now feeds payload-complete snapshots through the shared
 `pp_paint_renderer::prepare_document_frame_export_readiness` report, which
 records renderer-neutral six-face texture upload commands and encodes the
 active document frame's six composited faces to PNG bytes. This gives CLI
@@ -2304,6 +2308,11 @@ Results:
   the same save-writer route, and payload-complete snapshots now run the pure
   `pp_document` PPI exporter and decoded-project summary before emitting
   `ppiExport` JSON.
+- `pano_cli plan-canvas-project-save-target` now exposes the app-core planner
+  for retained project-save target paths, including the target PPI path,
+  temporary `.tmp.ppi` path, and timelapse `.pptl` sidecar. The live
+  `Canvas::project_save_thread` consumes the same planner before retained
+  serialization, reducing inline path compatibility logic in the legacy writer.
 - The same payload-complete snapshot automation now uploads the active document
   frame through `pp_paint_renderer::upload_document_frame_faces` and the
   `RecordingRenderDevice`, emitting `rendererUpload` JSON with texture,