Treat order as presentation in seed logic; add per-seed restore and routine duplication

Drag-to-reorder writes Routine.order through the document, which used to
read as a content edit: isPristine would fork a starter for a mere reorder,
and reconcile's semantic compare would clobber a reordered seed file back
to bundle order. Both now normalize order (and updatedAt) away — a fixed-
ULID file still never holds user content; ordering is bookkeeping.

SyncEngine gains restoreSeed(id:) — the per-seed analog of the bulk
restore, sharing one restoreSeedIfEligible core — and duplicate(routine:),
which copies any routine (starter or not) to a fresh ULID with fresh
exercise ids, a unique "… Copy" name, and last position in the list.

Claude-Session: https://claude.ai/code/session_01H8VxUX4ckjU3vRF5M4L5FV

WorkoutsTests/SeedLibraryTests.swift

@@ -93,6 +93,36 @@ struct SeedLibraryTests {
         #expect(!SeedLibrary.isPristine(edited))
     }
 
+    /// Dragging a starter to reorder the Library list writes a new `order` to it. Order
+    /// is presentation, not content, so a reorder must NOT fork the seed — an order-only
+    /// change reads as pristine.
+    @Test func pristineIgnoresOrderOnlyChange() throws {
+        let seed = try #require(SeedLibrary.seeds.first)
+        var edited = seed.doc
+        edited.order += 5
+        #expect(SeedLibrary.isPristine(edited))
+    }
+
+    /// A reorder save also stamps `updatedAt`; order + updatedAt together must still read
+    /// as pristine so a drag never forks a starter.
+    @Test func pristineIgnoresOrderAndUpdatedAtChange() throws {
+        let seed = try #require(SeedLibrary.seeds.first)
+        var edited = seed.doc
+        edited.order += 3
+        edited.updatedAt = Date()
+        #expect(SeedLibrary.isPristine(edited))
+    }
+
+    /// Order tolerance must not mask a genuine content edit: a real change (here, a
+    /// different rest length) is still detected even when `order` also differs.
+    @Test func pristineDetectsContentChangeDespiteOrderChange() throws {
+        let seed = try #require(SeedLibrary.seeds.first)
+        var edited = seed.doc
+        edited.order += 2
+        edited.restSeconds = (seed.doc.restSeconds ?? 60) + 30
+        #expect(!SeedLibrary.isPristine(edited))
+    }
+
     /// A non-seed id has no seed to compare against; `isPristine` defaults to
     /// true since callers are expected to gate on `isSeed` before asking.
     @Test func pristineDefaultsTrueForNonSeedID() throws {