verification: the tie patch test

An oracle case of uniaxial tension across a tie of non-matching meshes; the tie formulation
in docs/fem.md and the literature survey; ROADMAP M7 and parity updated.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01UhhZMBTviDQxZvwnyP89fo

tests/oracle/tie-patch/fixture.json

@@ -0,0 +1,33 @@
+{
+  "note": "FieldCraft's accepted results for this case, written by `cargo xtask oracle --bless`. A result outside its band fails CI.",
+  "values": {
+    "sxx_14": {
+      "band": 1e-9,
+      "value": -5.317400101732486e-15
+    },
+    "szz_1": {
+      "band": 1.0000000000000018e-8,
+      "value": 10.000000000000018
+    },
+    "szz_10": {
+      "band": 1e-8,
+      "value": 9.999999999999993
+    },
+    "szz_14": {
+      "band": 1.0000000000000002e-8,
+      "value": 10.000000000000002
+    },
+    "szz_19": {
+      "band": 1.0000000000000017e-8,
+      "value": 10.000000000000016
+    },
+    "szz_26": {
+      "band": 1.000000000000001e-8,
+      "value": 10.000000000000009
+    },
+    "uz_interface": {
+      "band": 1.0000000000000001e-11,
+      "value": 0.009999999999999997
+    }
+  }
+}