chore: repoint remaining links at git.swaits.com

Rewrites lingering github.com / *.sr.ht references to this Gitea instance,
translating GitHub and Sourcehut URL shapes to Gitea's (/blob/<ref>/ and
sr.ht /tree/<ref>/item/ -> /src/branch/<ref>/, /tree/<tag> -> /src/tag/<tag>,
/actions/workflows/X -> /actions?workflow=X, /edit/ -> /_edit/).

Left pointing at the old hosts on purpose: pull-request links (PRs were not
migrated), forks that were never migrated, and GitHub-only surfaces Gitea
lacks. OpenPGP identity proofs are untouched by design.

versions/v0.1.0/15-identity.md

@@ -81,7 +81,7 @@ Hex representation uses uppercase characters with 2 hex digits per byte.
 - [Section 3: Path](03-path.md) — Hash size in path encoding
 - [Section 5: Advertisement](05-payload-advert.md) — Signature usage
 - [Section 14: Cryptography](14-crypto.md) — Shared secret usage
-- Test vectors: [`corpus/crypto/ed25519/`](https://github.com/swaits/meshcore-spec/tree/main/versions/v0.1.0/corpus/crypto/ed25519/), [`corpus/crypto/ecdh/`](https://github.com/swaits/meshcore-spec/tree/main/versions/v0.1.0/corpus/crypto/ecdh/)
+- Test vectors: [`corpus/crypto/ed25519/`](https://git.swaits.com/swaits/meshcore-spec/src/branch/main/versions/v0.1.0/corpus/crypto/ed25519/), [`corpus/crypto/ecdh/`](https://git.swaits.com/swaits/meshcore-spec/src/branch/main/versions/v0.1.0/corpus/crypto/ecdh/)
 
 ### Reference Implementation