docs: archive Phase R (R1-R3) to COMPLETED; reconcile CLAUDE.md + CONTEXT.md

CONTEXT.md

@@ -958,7 +958,9 @@ pure/shell split as `bank_model` / `view_mode_model` / `bank_book`.
   back to unlink — behind the dry-run + confirm guardrail — only where the platform
   affords no portable trash. "Delete where possible" means recoverable-trash-
   preferred, never plain unlink-by-default. The move-to-trash surface is an explicit
-  per-platform **to-verify** (see REAPER/platform API surface).
+  per-platform **to-verify** (see REAPER/platform API surface). (R3 verified: Windows
+  `SHFileOperationW` + `FOF_ALLOWUNDO` confirmed against SDK 10.0.26100; macOS/Linux
+  unlink fallback — no portable SWELL trash surface.)
 - **Manual, explicit trigger (fork R-E, SETTLED 2026-07-24 — manual action + panel
   button).** Prune runs via a bindable manual action (dry-run-first, confirm-to-
   delete) **and** a `bank_panel` button that fires that same action — never a silent
@@ -1000,6 +1002,9 @@ No new REAPER *audio* API. New surfaces to verify before use:
   `SHFileOperation`, macOS `NSFileManager trashItemAtURL:`, Linux XDG trash spec).
   This is a **must-verify per platform** before use, not an assumed capability;
   where it is unavailable, fall back to unlink behind the dry-run/confirm guardrail.
+  (R3 verified: Windows routes to Recycle Bin via `SHFileOperationW` + `FOF_ALLOWUNDO`,
+  verified against SDK 10.0.26100. macOS / Linux: no portable SWELL trash surface
+  found — fall back to `unlink` behind the dry-run/confirm guardrail, as specified.)
 - **Owned-file manifest persistence (fork R-D, settled)** — a new tracked set in
   the `"reasampler"` ext-state (a sibling key or folded into the `banks` blob —
   build-time residual); shared M4 blob machinery, new data only. **Written from