feat(swift): lexical scope chain with graph-backed naming and resolution

[kafkas]

Description

Linear ticket: FER-7122

This PR is a foundational refactor of naming and reference resolution in the Swift generator. We replace the prior flat, name-only registry with a graph-backed name registry built on a lexical scope chain. During a single discovery pass, every symbol (modules, schema types, nested discriminated union variants, etc.) is registered as a node in the graph. All references are then resolved through the graph and emitted via swift.TypeReference.

We aim to emit concise identifiers like String and Int when unambiguous; when ambiguity or shadowing exists (e.g., nested user types colliding with Foundation), the resolver deterministically disambiguates and renames them. This is a major change that unifies registration, lookup, and emission under a single, scope-aware system.

Changes Made

• Extended as-is file definitions to include the shapes of exported symbols so they can be precisely registered in the new registry.
• Updated AbstractSwiftGeneratorContext to register the symbols to the new name registry and replace getSwiftTypeForTypeReference with getSwiftTypeReferenceFromScope that computes the type reference based on the current lexical scope.
• Added Referencer, responsible for constructing swift.TypeReference instances from a given symbol scope; all cross-scope lookups now route through it.
• Removed the old SourceSymbolRegistry and TestSymbolRegistry in favor of the graph-backed NameRegistry.
• Introduced the TypeReference AST node, which carries a resolved reference to a symbol and is used when rendering types.
• Updated various AST nodes like ComputedProperty, Expression, Method to use TypeReference instead of Type during emission.
• Added the swift.Symbol class to represent a symbol in a project with a unique ID, name and some helper methods
• Added swift.Symbol to represent a symbol with a stable ID, human-readable name, and helpers for generators.
• Added SymbolGraph to store the Symbol nodes for a given project and resolve references according to a lexical scope chain
• Added SymbolRegistry, a low-level registry primitive that internally relies on a SymbolGraph
• Deleted LocalContext, LocalSymbolRegistry in favor of the new name registry.
• Updated SDKGeneratorCli and all generators like StructGenerator, DiscriminatedUnionGenerator, WireTestSuiteGenerator etc. to pull the names from the new registry and use the scope-aware Referencer to create resolved type references.
• Deleted getQueryParamCaseName that relied on swift.Type in favor of the EndpointMethodGenerator.inferQueryParamCaseName() that relies on swift.TypeReference
• Minor changes in core-utils to add new assertion types and export all assertion utils from assert.ts
• Updated Seed snapshots

Testing

• Unit tests added/updated
• Manual testing completed