Adding and Implementing Zod

- [ ] **Add Zod schemas for codemeta and code.json**
- Define Zod schemas that describe valid input for each format. Use them to parse and validate input inside the coordinator functions before the engine runs.
- ***Acceptance:*** Malformed input produces a Zod validation error with a readable message identifying the offending field, rather than silently producing garbage output.

- [ ] **Validate converted output against the target schema**
- After `convert` returns, validate the result against the target format's Zod schema. Decide whether invalid output throws or returns a warnings array, and document the choice.
- ***Acceptance:*** A transform that returns an incorrectly shaped value is caught by output validation in a test, and the behavior (throw vs warn) is documented in the API docs.

- [ ] **Type the transform functions properly**
- Replace `(value: unknown) => unknown` signatures with types derived from the Zod schemas, so transforms declare what they accept and return.
- ***Acceptance:*** A transform with a mismatched input or output type produces a compile-time TypeScript error, and all existing transforms have typed signatures.

- [ ] **Emit a conversion report alongside converted output**
- Produce a structured report describing which source fields were ignored, which target fields were filled with defaults, and any lossy transforms that ran. The report can be opt-in or always returned.
- ***Acceptance:*** Callers can obtain a report for any conversion, and at least one test asserts on report contents for a known-lossy input (e.g. multi-author codemeta → code.json).