feat(core,view): input cards with change tracking (plan B1 · C2)

- Three values per pier: defaults (as imported), input (generated), draft
  (current cards). Overrides = draft vs defaults; pending = draft vs input.
- Editable now: 코핑 폭, 코핑 길이, 말뚝 길이. Changing a card does not touch the
  3D view until 다시 생성; the header and the card show 변경 n.
- Revert puts a field back to its imported default.
- Project files store defaults and draft (optional; v1 files still open).
- Tests: 코핑 폭 3100 → 3300 gives one override and one pending change;
  regenerating clears pending but keeps the override; revert; file round trip.
- Not verified in a browser (no debuggable Chrome in this session).

Co-Authored-By: Claude Haiku 5.5 <noreply@anthropic.com>

src/core/project.ts

@@ -14,8 +14,12 @@ export interface ProjectInfo {
 
 export interface ProjectPier {
   id: string;
-  /** Input as read from the spreadsheet. The 3D model is not stored; it is regenerated on open (spec §8). */
+  /** Generated input: the values the 3D model was built from. The model is not stored; it is regenerated on open (spec §8). */
   input: PierInput;
+  /** Values as imported from the sheet (기본값). Missing in files saved before change tracking: input is used. */
+  defaults?: PierInput;
+  /** Values currently in the cards (현재 입력). Missing in older files: input is used. */
+  draft?: PierInput;
 }
 
 export interface ProjectFile {
@@ -54,6 +58,11 @@ export function parseProject(text: string): ProjectFile {
     if (typeof input.name !== 'string' || !Array.isArray(input.ips) || !Array.isArray(input.bearings)) {
       throw new Error(`교각 ${i + 1}(${String(input.name)}): 입력 형식이 맞지 않습니다.`);
     }
+    for (const extra of [p.defaults, p.draft]) {
+      if (extra !== undefined && (typeof extra !== 'object' || extra === null || typeof extra.name !== 'string')) {
+        throw new Error(`교각 ${i + 1}(${input.name}): defaults 또는 draft 형식이 맞지 않습니다.`);
+      }
+    }
   });
   return obj as ProjectFile;
 }