port: land the loop decode on the handoff, and note the edit trap

Second iteration running where a scripted HANDOFF edit failed its
assertion on rewrapped text, leaving the port's page stale while docs/re
had the finding. Patched by reading the file first, and METHOD now says
to check the commit's file count for a silently dropped edit.

docs/port/HANDOFF.md

@@ -65,12 +65,15 @@ authored version can be deleted.
   luminance oscillates continuously at **≈ 2.2 s ± 0.4** (measured, 7 intervals
   over a 22 s capture). Build 4 declares `ptloop01.rat`/`ptloop02.rat`, and
   `loop*.rat` is a decoded **looping sprite animation**. Drawing the resting
-  pose and stopping will look wrong. ❔ Whether 2.2 s is the loop's declared
-  cycle is **still unread**. The record was located — an `opt `-linked `RATC` at
-  `0xbb5966` in build 4, placing `pteff03.t32`, declaring 30 at `+0x004`, with a
-  pivot matching `screen info` — but a leaf record's keyframe times are **not** in
-  the build's 40-byte block layout, and a strided monotonic scan finds nothing.
-  The period is measured; the port hardcodes it.
+  pose and stopping will look wrong.
+  ✅ **The loop records are decoded**: `ptloop01.rat` (an `opt `-linked `RATC` at
+  `0xbb5966`) sweeps `pteff03.t32` left→right over **450 units = 7.5 s**;
+  `ptloop02.rat` sweeps `pteff03a.t32` right→left over **570 units = 9.5 s**.
+  Ordinary 40-byte keyframe blocks from `+0x68`, three keyframes each.
+  ❔ **But those are not the ≈ 2.2 s oscillation** — a 7.5 s cycle gives ~3 peaks
+  in a 22 s capture and it showed 8. The 2.2 s period is real and its **source is
+  unidentified**, so expect the title to carry *both* the decoded sweeps and
+  something else.
 * **Menu order is geometric.** Buttons sorted top-to-bottom by resting Y. This is
   ✅ correct for a vertical menu and is **not** a decoded neighbour graph — the
   disc's real navigation structure is unknown, and `opt ` is *not* a focus link