TypeScript migration: add reporter and game API boundary types

[KagamiChan]

Context

The mechanical TypeScript source move and tsdown build are already in place. The next migration slice is to introduce shared boundary types without changing reporter behavior.

Reference: docs/typescript-migration-plan.md PR 4.

Scope

• Add shared reporter/game API/window-state type modules, such as:
  • src/types/reporter.ts
  • src/types/game-api.ts
  • src/types/window-state.ts
• Define GameResponseEventDetail for game.response payloads: method, path, body, postBody, and time.
• Define a shared Reporter interface and make reporter classes conform to it.
• Type BaseReporter.report and BaseReporter.getJson.
• Add narrow boundary helpers such as asRecord, parseInt10, getWindowShip, and getWindowSlotItem.
• Keep Kancolle response bodies as unknown or coarse local interfaces at unsafe boundaries until each reporter is typed.

Acceptance criteria

• Entry/runtime and base reporter boundaries are typed.
• Reporter classes conform to a shared interface.
• No reporter payload field names or endpoint behavior changes.
• No broad catch/silent fallback behavior is introduced.

Validation

• pnpm run typecheck
• pnpm run build