[jeremycare]

Replace tsyringe with a Map-based registry

Summary

The container only used a small, non-decorator slice of tsyringe: isRegistered, register, resolve, reset, plus Lifecycle.Singleton and instanceCachingFactory. All of that reduces to "look up by token, instantiate once, cache". This PR replaces it with a single Map keyed on the Token instance itself, and drops both runtime dependencies.

The package now has zero runtime dependencies.

What changed

• New container.ts: a module-level Map<Token, Entry> with has, set, resolve, and clear. Every provider kind (useValue, useClass, useFactory) resolves lazily on first inject and is cached afterwards, matching the previous singleton and caching-factory behavior.
• Token.ts: no longer allocates a Symbol. The token object is the registry key, so identity and uniqueness come from the instance. A name field replaces the symbol description for error messages, and a phantom __type field keeps Token<A> and Token<B> non-interchangeable at the type level.
• register.ts, inject.ts, reset.ts: thin wrappers over the new module. Public signatures and JSDoc are unchanged.
• index.ts: removes the reflect-metadata side-effect import.
• package.json: removes tsyringe and reflect-metadata, drops the tsyringe keyword, updates the description.
• tsconfig.json: removes experimentalDecorators and emitDecoratorMetadata, which nothing used.
• README.md: no longer describes the package as a Tsyringe wrapper.
• di-container.test.ts: adds coverage for the behavior previously delegated to tsyringe (see Testing).

Why

• The ClassProvider type is new () => T, so constructor injection was never possible through this API. The README already recommends inject() as a property initializer instead of constructors. Decorator metadata and reflect-metadata were dead weight.
• Removing tsyringe removes a transitive install for every consumer and the reflect-metadata global polyfill side effect.

Breaking changes

• Token.symbol is removed. Use Token.name for a readable label.
• The package no longer imports reflect-metadata. Consumers who relied on this package to polyfill Reflect.metadata for their own decorators must import it themselves.
• The error message for resolving an unregistered token now reads Attempted to resolve unregistered token <name>. instead of tsyringe's wording.

This warrants a major version bump.

Testing

• tsc --noEmit: no errors
• jest: 15 passed, 0 failed (8 existing, 7 new)
• New tests cover:
  • useClass and useFactory providers resolve exactly once and return the same instance
  • class providers are instantiated lazily on first inject
  • default providers register on first inject and yield to explicit registrations
  • tokens with identical names are distinct registrations
  • Token<A> is not assignable to Token<B>, enforced via @ts-expect-error under ts-jest