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/changes.ts

@@ -0,0 +1,45 @@
+import type { PierInput } from './types';
+
+/**
+ * Inputs the user can change on the 2단계 cards (spec §5.2 · plan C2). Each one maps to a field of PierInput.
+ * Extend this list as more cards are enabled; the tracking below works on any of these keys.
+ */
+export const EDITABLE_FIELDS = [
+  { key: 'copingWidthMm', label: '코핑 폭 B', unit: 'mm' },
+  { key: 'copingLengthMm', label: '코핑 길이 L', unit: 'mm' },
+  { key: 'pileLengthMm', label: '말뚝 길이', unit: 'mm' },
+] as const;
+
+export type EditableKey = (typeof EDITABLE_FIELDS)[number]['key'];
+
+/** Keys whose values differ between two inputs. */
+export function changedKeys(a: PierInput, b: PierInput): EditableKey[] {
+  return EDITABLE_FIELDS.map((f) => f.key).filter((key) => a[key] !== b[key]);
+}
+
+/**
+ * The three values a pier carries while it is edited (spec §5.5, plan B1):
+ * - defaults: the values as imported from the sheet (기본값, shown as "기본 3100").
+ * - input: the values the 3D model was generated from (생성본).
+ * - draft: the values the user currently has in the cards (현재 입력).
+ */
+export interface PierValues {
+  defaults: PierInput;
+  input: PierInput;
+  draft: PierInput;
+}
+
+/** Overrides: draft differs from the imported default (주황 표시, "변경 n건" in the card). */
+export function overrideKeys(p: PierValues): EditableKey[] {
+  return changedKeys(p.defaults, p.draft);
+}
+
+/** Pending: draft differs from the generated model, so the 3D view is out of date (미반영 변경). */
+export function pendingKeys(p: PierValues): EditableKey[] {
+  return changedKeys(p.input, p.draft);
+}
+
+/** Puts one field back to its imported default in the draft. */
+export function revertDraft(p: PierValues, key: EditableKey): PierInput {
+  return { ...p.draft, [key]: p.defaults[key] };
+}

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;
 }