feat: Migrate workflow discovery from TypeScript to Oxc

[eersnington]

Summary

• Replaces TypeScript parser-based workflow discovery with an Oxc parser adapter.
• Uses Oxc raw-transfer when supported and falls back to standard Oxc parsing otherwise.
• Parses Oxc output into Sideffect-owned workflow AST types before analysis.
• Models discovery failures with Effect tagged errors and translates them to Vite build errors at the boundary.
• Keeps collectWorkflowEntries() synchronous and avoids leaking Vite diagnostics callbacks into the public API.
• Adds Vite logging for the selected workflow discovery parser.
• Adds regression coverage for empty re-exports so export {} from "./x" is not treated as export *.

Validation

• bun run --cwd packages/sideffect check
• bun run --cwd packages/sideffect test
• bun run check
• bun run test
• bun run build:sideffect