fix(01): revise plans based on checker feedback

- 01-01: Reframe must_haves.truths to user-observable behaviors
- 01-01: Remove unimplemented key_link (wiring happens in later phases)
- 01-02: Add test case for DATA-04 (custom items at any position)
- 01-02: Add must_haves.truths entry for custom item flexibility
- 01-02: Document LocalItineraryItem is standalone (no sibling models needed)

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

.planning/phases/01-semantic-position-model/01-01-PLAN.md

@@ -11,9 +11,9 @@ autonomous: true
 
 must_haves:
   truths:
-    - "Games get sortOrder derived from game time (minutes since midnight + offset)"
-    - "Inserting between two items produces midpoint sortOrder"
-    - "Day number can be calculated from any date given trip start date"
+    - "Games sort by schedule time within each day"
+    - "Items can be inserted at any position (before, between, after existing items)"
+    - "Items can be assigned to any trip day by date calculation"
   artifacts:
     - path: "SportsTime/Core/Models/Domain/SortOrderProvider.swift"
       provides: "sortOrder calculation utilities"
@@ -21,11 +21,7 @@ must_haves:
     - path: "SportsTime/Core/Models/Domain/Trip.swift"
       provides: "Day derivation methods"
       contains: "func dayNumber(for date: Date) -> Int"
-  key_links:
-    - from: "SortOrderProvider"
-      to: "ItineraryItem.sortOrder"
-      via: "Utilities compute values assigned to sortOrder property"
-      pattern: "sortOrder.*=.*SortOrderProvider"
+  key_links: []
 ---
 
 <objective>