refactor: split transformer.ts into smaller modules

[barispe]

Problem

src/transformer.ts is currently 2,303 lines - the largest file in the codebase by far. It handles all Cypress-to-Playwright chain conversions in a single file, making it difficult to navigate, test, and maintain.

Proposed Solution

Split transformer.ts into focused, single-responsibility modules:

Suggested structure

src/ transformer/ index.ts # Public API (transformFile, parseCustomCommands) chain-converter.ts # convertCypressChain - the core dispatch logic chains/ get-chain.ts # convertGetChain (~300 lines) url-chain.ts # convertUrlChain (~50 lines) title-chain.ts # convertTitleChain (~40 lines) cy-on.ts # convertCyOn (~70 lines) cy-stub.ts # convertCyStub (~90 lines) cy-request.ts # convertCyRequest (~290 lines) assertions/ should-converter.ts # convertShouldAssertion (~100 lines) blocks/ block-accumulator.ts # accumulateBlock intercept-handler.ts # convertCyIntercept wait-handler.ts # convertCyWait each-handler.ts # convertCyEach window-handler.ts # convertCyWindow within-handler.ts # convertCyWithin custom-commands.ts # CustomCommandDef, parseCustomCommands types.ts # ChainCall, ChainConversionResult, etc. utils.ts # Shared helpers (quote stripping, indent, etc.)

Benefits

• Readability: Each file is focused on one conversion type
• Testability: Individual chain converters can be unit tested in isolation
• Maintainability: Adding new chain converters doesn't bloat a single file
• Discoverability: New contributors can find what they need quickly

Migration Plan

1. Create the src/transformer/ directory structure
2. Extract chain converters one at a time (start with the smallest)
3. Keep the public API (transformFile, parseCustomCommands) stable via re-exports from index.ts
4. Update imports across the codebase
5. Run full test suite after each extraction to verify nothing breaks

Acceptance Criteria

• No single file exceeds ~400 lines
• All existing tests pass without modification
• Public API remains unchanged (no breaking import changes for consumers)
• Each extracted module has clear JSDoc comments