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/README.md

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+# Tie patch test (non-matching meshes)
+
+Two unit cubes stacked along z, meshed independently: 3 × 3 × 2 hex8 below (graded in x and y),
+2 × 2 × 2 above, so the nodes at z = 1 do not match. A tie bonds the upper block's bottom
+(secondary) to the lower block's top (main). The faces x = 0 and y = 0 are symmetry planes, the
+base z = 0 is held in z, and the top z = 2 is pulled up by 0.02 (E = 1000, ν = 0.3) in a linear
+static step. The exact state is the uniaxial stress σ_zz = 10, uniform in both blocks.