Add skills to translate SDK resources to framework resources

[remyleone]

It would be helpful to have skills to help to translate existing SDK resources to framework resources.

[AdamTylerLynch]

PR #86 adds a dedicated provider-framework-migration skill for exactly this: muxing SDKv2 + Framework in one provider (tf5to6server + tf6muxserver main.go), a per-resource migration workflow (baseline tests first, blocks stay blocks, keep the exact schema, move registration last), an SDKv2→Framework schema/data-access translation table, and the null-vs-zero behavioral trap that makes naive translations silent breaking changes. It also encodes the don't-migrate-complex-resources triage policy from terraform-provider-aws.