Fix C++ literal parser to match Python concore wire format

[GaneshPatil7517]

Hey @pradeeban Sir
Fixes #389 The C++ parser() in concore.hpp previously used std::stod() on every comma-separated token, which silently crashed on valid concore payloads containing strings, booleans, nested lists, or tuples that Python nodes produce via ast.literal_eval().

This PR replaces the stod-only parser with a minimal recursive descent parser that supports the full Python literal wire format, restoring cross-language compatibility.

Changes

concore_base.hpp

• ConcoreValue type — A discriminated union (NUMBER, BOOL, STRING, ARRAY) mirroring Python's ast.literal_eval() output
• Recursive descent parser (parse_literal_value, parse_literal_string, parse_literal_array) handling:
  • Numbers (int, float, negative, scientific notation)
  • Booleans (True/False → 1.0/0.0)
  • Strings (single/double quoted with escape sequences)
  • Nested arrays and tuples (treated identically)
  • None (treated as string "None")
  • Trailing commas
• flatten_numeric() — Recursively extracts all numeric values from a ConcoreValue
• parselist_double() — Now delegates to the full parser; falls back gracefully on edge cases

concore.hpp

• Exposed parse_literal() and flatten_numeric() methods on the Concore class
• Existing parser() method unchanged in signature — full backward compatibility

TestLiteralEvalCpp.cpp (new)

• 79 tests covering:
  • Backward compatibility (flat numeric, empty, negative, scientific notation)
  • Mixed-type payloads: [10.0, "start", 0.5], [10.0, True, 0.5], [10.0, [0.5, 0.3], 0.1], (10.0, 0.3)
  • Full ConcoreValue structure verification
  • Error handling (malformed brackets, unterminated strings, unsupported objects)
  • Cross-language round-trip (Python write → C++ read)

README.md

• Added Wire Format section documenting the concore payload specification

Before / After

Payload	Before (C++)	After (C++)
[10.0, 0.5]	✅ Works	✅ Works
[10.0, "start", 0.5]	❌ std::invalid_argument	✅ [10.0, 0.5] (string skipped)
[10.0, True, 0.5]	❌ Crash	✅ [10.0, 1.0, 0.5]
[10.0, [0.5, 0.3], 0.1]	❌ Crash	✅ [10.0, 0.5, 0.3, 0.1]
(10.0, 0.3)	❌ Empty	✅ [10.0, 0.3]

Testing

$ g++ -std=c++11 -o TestLiteralEvalCpp TestLiteralEvalCpp.cpp && ./TestLiteralEvalCpp
Results: 79 passed, 0 failed out of 79 tests

Per @pradeeban Sir instruction: this PR addresses the C++ implementation only. Verilog is not modified.