feat(solidity): add direct persistent-state reads and writes

[tob-scott-a]

Add a Solidity-first state web for #71. A function such as transfer now has READS/WRITES edges to persistent storage declarations such as token:Token.balances, with a location for each source occurrence. State queries return distinct declarations or readers/writers, while default call traversals remain unchanged.

The parser handles assignments, compound assignments, increments, deletes, struct/mapping/array accesses, direct array push/pop, and lexical shadowing. Constants, immutables, and transient variables are excluded. Model, storage, query, parser, JSON export, README, and snapshot coverage are included.

Scope: direct accesses to storage declared in the same contract. Inherited state, alias propagation, library/assembly/delegatecall effects, declaration initializers, generated getters, and transitive modifier effects are documented limitations. Other language adapters remain follow-up work, so this references rather than closes #71.

Validation:

• Full pytest suite: 1,440 passed.
• Ruff lint/format and ty: passed.
• Focused mutation campaign using tests.run_mutations: 33/35 killed, with clean and instrumented baselines passing. The two surviving mutations change defensive declaration-field and expression-wrapper guards.
• Dependency setup used the checked-in lockfile with uv --frozen because the local global exclude-newer setting predates a required locked dependency.