add vdi2230 skill: VDI 2230 bolt joint dimensioning engine

Full R0-R13 calculation engine with:
- Guided data collection (N bolts, per-bolt load, DA_prime, thermal dT)
- Auto-sizing script (M4->M39 iteration across strength classes)
- fm_table A1 lookup for fast MA/FM queries without full R0-R13
- Warnings for stainless steel galling, ESV insert threads (Helicoil/Ensat)
- Bolt circle load distribution formula (FA + MB + MT)
- 7 evals covering static, fatigue, ESV aluminium, pressure seal,
  thermal steel-aluminium, and combined FA+FQ cases

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

vdi2230/scripts/example_input.json

@@ -0,0 +1,55 @@
+{
+  "_comment": "Esempio input VDI 2230 — Giunzione flangia flangia, M12 10.9, DSV, carico alternato",
+  "_units": "Forze in N, lunghezze in mm, pressioni in N/mm², temperature in K",
+
+  "size": "M12",
+  "strength_class": "10.9",
+  "thread_type": "coarse",
+  "joint_type": "DSV",
+
+  "lK_mm": 40,
+  "DA_mm": 36,
+  "dh_mm": 13.5,
+  "DA_prime_mm": 60,
+  "hmin_mm": 20,
+
+  "ssym_mm": 0,
+  "a_mm": 0,
+  "n_factor": 1.0,
+  "IBers_mm4": 0,
+
+  "FA_max_N": 20000,
+  "FA_min_N": 5000,
+  "FQ_max_N": 0,
+  "MY_max_Nmm": 0,
+
+  "mu_G": 0.12,
+  "mu_K": 0.12,
+  "mu_T": 0.12,
+  "qF": 1,
+  "qM": 1,
+  "ra_mm": 0,
+
+  "pi_max_N_mm2": 0,
+  "AD_mm2": 0,
+  "IBT_mm4": 0,
+  "u_mm": 0,
+  "MB_max_Nmm": 0,
+
+  "alpha_A": 1.7,
+
+  "EP_N_mm2": 210000,
+  "pG_N_mm2": 900,
+
+  "fZ_total_um": 12,
+  "alpha_S": 1.15e-5,
+  "alpha_P": 1.15e-5,
+  "dT_S_K": 0,
+  "dT_P_K": 0,
+
+  "meff_actual_mm": 20,
+  "internal_material": "steel",
+  "thread_treatment": "SV",
+
+  "lGew_mm": 5
+}