add SPICE subcircuit import dialog

[esaruoho]

Summary

Ports the origin/spiceimport branch to v3-dev. Adds File > "Import Subcircuit From Spice..." which opens a dialog where users can paste SPICE netlist text to create a CircuitJS1 subcircuit model.

Supported SPICE elements

• Passive: R (resistor), C (capacitor), L (inductor)
• Semiconductor: D (diode with .model), Q (BJT with area scaling, parasitic RC/RB/RE, junction CJE/CJC), J (JFET with VTO/BETA)
• Sources: V (voltage), I (current)
• Controlled sources: E (VCVS), G (VCCS), H (CCVS), F (CCCS), B (behavioral)
• Directives: .model (NPN/PNP/D/NJF/PJF), .subckt/.ends, .rename
• Advanced: POLY() polynomial sources, VALUE={expression} syntax, continuation lines (+), area-scaled transistor model variants

Changes

• 2 new files: BetterStringTokenizer.java (flexible SPICE tokenizer), ImportFromSpiceDialog.java (695-line parser and dialog)
• Menus.java — add "Import Subcircuit From Spice..." menu item
• CommandManager.java — add importfromspice command handler
• CustomCompositeModel.java — add setName() to ExtListEntry (for .rename directive)
• EditCompositeModelDialog.java — add loadModel() method and defaultName field for external model loading (used by SPICE importer to bypass createModel() which requires an existing circuit)
• TransistorModel.java — fix getModelWithName() to use 2-arg constructor TransistorModel(name, 1e-13) instead of no-arg constructor, ensuring proper initialization of emission coefficients and other defaults

Test plan

• File > Import Subcircuit From Spice — verify dialog opens
• Paste a simple SPICE subcircuit (e.g. voltage divider) — verify it creates a subcircuit model
• Paste a BJT amplifier subcircuit with .model — verify transistor parameters are imported
• Paste a subcircuit with controlled sources (E, G) — verify expression parsing
• Paste a subcircuit with POLY() controlled sources — verify polynomial conversion
• Verify the pin layout dialog opens with correct pin count and default name
• Verify existing subcircuit creation (File > Create Subcircuit) still works

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