[jdjioe5-cpu]

Summary

Fixes #2438
Also addresses #691

When a Soroban contract function declares return or input parameters typed as generic Val (represented as SC_SPEC_TYPE_VAL / ScType::Val in contract specs), calling the function or passing parameters via stellar contract invoke caused panics or parsing failures:

1. Output formatting: Returning Bool(false) or other primitives previously panicked with not yet implemented: Bool(false,) doesn't have a matching Val or InvalidPair(..., Val) when falling through spec object dispatch.
2. Argument parsing: from_json fell back directly to serde_json::from_value which fails on primitive JSON values like booleans, integers, or bare strings for ScType::Val.

Changes

• cmd/crates/soroban-spec-tools/src/lib.rs:
  • Implemented val_from_json to recursively infer and convert any JSON value (null/void, bool, numbers, addresses, strings, arrays, objects) to its corresponding ScVal representation, while maintaining backwards compatibility with serialized ScVal formats.
  • Added (ScType::Val, _) => val_from_json(v)? in Spec::from_json.
  • Added fallback string parsing for ScType::Val in Spec::from_string.
  • Added (val, ScType::Val) => to_json(val)? safeguard in Spec::sc_object_to_json.
  • Provided descriptive placeholders in arg_value_name (Some("val")) and example (Some("\"any_value\"")).
  • Added regression unit tests for ScVal::Bool(false)/true, all scalar variants, bare strings, numbers, and collections with ScType::Val.
• cmd/soroban-cli/src/commands/contract/arg_parsing.rs:
  • Registered ScSpecTypeDef::Val in is_primitive_type to allow natural command-line inputs.
  • Added context suggestions for ScSpecTypeDef::Val.
  • Added unit test test_val_arg_parsing verifying argument parsing for booleans, integers, and strings.

Evidence

• cargo fmt --check --all: Passed (0 errors).
• cargo test -p soroban-spec-tools: 113/113 passed.
• cargo test -p soroban-cli --lib commands::contract::arg_parsing: 31/31 passed.