feat(types): add lexicon type generation

[skiniks]

This PR adds a script to automatically:

1. Download the latest lexicons from ATProto's repo
2. Generate TypeScript types using @atproto/lex-cli

Not ready for merge yet, but sharing for early feedback. Current status:

• ✅ Downloads latest lexicons from ATProto
• ✅ Extracts only lexicon files
• ✅ Generates types using official lex-cli
• ⏳ Need to decide on additional type enhancements (see @atcute/lex-cli)

Next steps:

• Evaluate if we want to add branded types (like @atcute/lex-cli)
• Add CI integration

related to #30

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[anbraten]

Just tried your PR and those types look really handy already. One thing I noticed is that it currently is based on @atproto/xrpc. Would it be possible to only export types in this package sth like an object mapping xrpc calls to params and repsonse types, without an underlying api client.

[bdbch]

LGTM - just two comments we could clarify. Cool idea!

[skiniks]

Closing this PR as its functionality has been superseded by #28 which was just merged.