feat(codegen): generate go doc comments for client wrappers from openapi spec

[tharropoulos]

Change Summary

• add typesense/api/generator/docgen.go post-pass that walks each wrapper file, resolves methods to operations via their apiClient.<Op> call, and injects doc comments above the impl and matching interface declaration
• wire docgen into typesense/api/generator/main.go after generateClient() so go generate produces hover docs from the openapi summary/description/method/path/tag
• annotate 30 wrapper files using the spec's verbatim text plus a See: link derived from the operation's tag
• hand-write hover docs and See: links for top-level Client accessor methods and the MultiSearch field in typesense/client.go

PR Checklist

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[tharropoulos]

some linting errors, will update and mark it for review

[tharropoulos]

CC: @kishorenc

[jamietanna]

This should be (mostly) available in upstream oapi-codegen now 🤞🏼