Explicit per-include dialect (lang=) for foreign netlist includes

[pepijndevos]

Summary

Enable VACASK include statements to explicitly name their foreign dialect (include "f" lang=ngspice section=tt) instead of inferring from file extension.

Changes

• Thread dialect param through mixed parser parse_spectre_with (removes hardcoded Dialect::Ngspice)
• Add dialect-string FFI: parse_netlist(src, language), parse_netlist_lib(src, section, language); removed parse_spectre_netlist
• Case-insensitive dialect names; demo + README updated
• Design spec + implementation plan included (docs/superpowers/)

Notes

• Rust-side plumbing only — no runtime ngspice→VACASK model translation
• Corresponding C++/lexer/bridge changes in VACASK repo (rust-parser-integration branch, PR #87)
• Tests: cargo test -p netlist-cxx (18 tests) + netlist-syntax suites all pass

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.

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