Add BOM output, fix LTspice Tier 2 import, real .asc integration tests

- Fix _try_ltspice_generation() to use spicelib.simulators.ltspice_simulator.LTspice
  instead of the abstract Simulator base class (which always returned unavailable)
- Use LTspice.create_netlist() instead of Simulator.run() for correct netlist generation
- Add --ltspice-exe CLI option to specify LTspice binary path
- Add --bom flag for component BOM CSV output (works on any parse completeness)
- Add --bom-wiring flag for wiring BOM CSV from mapped output
- Add real 1002A.asc demo circuit and pre-generated .net as test fixtures
- Add @pytest.mark.ltspice marker for tests requiring LTspice binary
- Bump version to 2026.2.14

tests/fixtures/1002A.net

@@ -0,0 +1,19 @@
+* Z:\tmp\1002A.asc
+* Generated by LTspice 26.0.1 for Windows.
+V1 +V 0 15
+V2 -V 0 -15
+R1 N003 N001 10K
+R2 N001 0 100K
+V3 IN- IN+ SINE(0 1m 100)
+R3 N002 N001 2.2K
+R4 N002 N003 10K
+R5 OUT N002 100K
+V4 IN+ 0 SINE(0 1 10)
+X§U1 IN- N001 +V -V N003 LT1001 ;§pnba In+)In-)V+)V-)OUT
+X§U2 IN+ N002 +V -V OUT LT1001 ;§pnba In+)In-)V+)V-)OUT
+.tran 300m
+* Two Op Amp Instrumentation Amplifier
+* Library below included based on ModelFile attribute of instance X§U1, X§U2 (C:\users\rpm\AppData\Local\LTspice\lib\sym\OpAmps\LT1002A.asy)
+.lib LTC.lib
+.backanno
+.end