feat: read concrete-lining drawings 04-004..009 and link lining spec to model (Task 6)

Extracted per-sheet pattern groups (입출구부 50 m / 온도미고려), note-5 scope,
fck 27 MPa, SD400, aggregate 25 mm, rebar label counts and printed radii.
Model keeps R1 = 6,982 mm; lining sheets print 6.892 m -> [CONFLICT DETECTED]
for user check. Sheet-to-station and pattern-name mapping left [미확정].
Viewer shows the lining spec on click.

Co-Authored-By: Claude Haiku 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01A5Cun3RHQKna9qxE6ybZ4A

model/tunnel_skeleton_meta.json

@@ -1874,6 +1874,82 @@
   "open": [
     "4+700~4+745 and 5+480~5+500 excluded ([미확정])",
     "pattern zones (03-003~008) pending Task 5",
-    "lining details (04-004~009) pending Task 6"
-  ]
+    "lining reference recorded (meta.lining_reference, 04-004~009); sheet-to-station mapping [미확정]",
+    "[CONFLICT DETECTED] lining sheets print R1=6.892 m, standard section R1=6,982 mm (model keeps 6.982) - user check"
+  ],
+  "lining_reference": {
+    "source": "C0060304-004..009 (콘크리트라이닝구조도)",
+    "concrete": "fck 27 MPa",
+    "rebar": "SD400 (fy 400 MPa)",
+    "aggregate_mm": 25,
+    "summary": "C0060304-004~009 | fck 27 MPa | SD400 | 입출구부 50 m 취약구간 철근 상세 (측점 대응 미확정)",
+    "sheets": [
+      {
+        "sheet": "C0060304-004-콘",
+        "groups": [
+          [
+            "A~C-2",
+            "입출구부 50m"
+          ]
+        ]
+      },
+      {
+        "sheet": "C0060304-005-콘",
+        "groups": [
+          [
+            "E-1~2",
+            "온도미고려"
+          ],
+          [
+            "D-1~2",
+            "입출구부 50m"
+          ]
+        ]
+      },
+      {
+        "sheet": "C0060304-006-콘",
+        "groups": [
+          [
+            "WL-1~2,RP-1~2",
+            "온도미고려"
+          ],
+          [
+            "E-1~2",
+            "입출구부 50m"
+          ]
+        ]
+      },
+      {
+        "sheet": "C0060304-007-콘",
+        "groups": [
+          [
+            "WL-1~2",
+            "입출구부 50m"
+          ],
+          [
+            "WL-3~4",
+            "온도미고려"
+          ]
+        ]
+      },
+      {
+        "sheet": "C0060304-008-콘",
+        "groups": [
+          [
+            "WL-3~4",
+            "입출구부 50m"
+          ]
+        ]
+      },
+      {
+        "sheet": "C0060304-009-콘",
+        "groups": [
+          [
+            "P-2~3",
+            "입출구부 50m"
+          ]
+        ]
+      }
+    ]
+  }
 }