refactor(web): extract drag position helpers

scripts/check-architecture-guardrails.mjs

@@ -292,6 +292,21 @@ export const rules = [
     ],
     forbidden: [],
   },
+  {
+    file: "apps/web/src/hooks/timelineDragPosition.ts",
+    maxLines: 80,
+    required: [
+      {
+        pattern: /\bexport function resolveProjectDragPosition\b/,
+        message: "timeline drag position helpers must keep project drag date derivation centralized",
+      },
+      {
+        pattern: /\bexport function resolveAllocationDragPosition\b/,
+        message: "timeline drag position helpers must keep allocation drag date derivation centralized",
+      },
+    ],
+    forbidden: [],
+  },
   {
     file: "apps/web/src/hooks/timelineDocumentDrag.ts",
     maxLines: 50,
@@ -383,6 +398,10 @@ export const rules = [
         pattern: /from "\.\/timelineDragCleanup\.js"/,
         message: "timeline drag must keep unmount teardown delegated to the extracted helper module",
       },
+      {
+        pattern: /from "\.\/timelineDragPosition\.js"/,
+        message: "timeline drag must keep project and allocation drag position derivation delegated to the extracted helper module",
+      },
       {
         pattern: /from "\.\/timelineDocumentDrag\.js"/,
         message: "timeline drag must keep document mouse listener lifecycle delegated to the extracted helper module",
@@ -433,6 +452,10 @@ export const rules = [
         pattern: /\bfunction attachDocumentMouseDrag\b/,
         message: "timeline drag must not re-inline extracted document listener helper implementations",
       },
+      {
+        pattern: /\bconst (?:deltaX|pointerDeltaX) = clientX - (?:drag|alloc)\.startMouseX;[\s\S]*computeDragDates\(/,
+        message: "timeline drag must not re-inline extracted project or allocation drag position helpers",
+      },
       {
         pattern: /\bfunction (?:isAllocationMultiSelected|startAllocationMultiDrag|updateAllocationMultiDrag|finalizeAllocationMultiDrag)\b/,
         message: "timeline drag must not re-inline extracted allocation multi-drag helper implementations",