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/v0.1.0/09-payload-path.md

@@ -82,7 +82,7 @@ hash is unique.
 - [Section 3: Path](03-path.md) — Path length encoding
 - [Section 6: Encrypted Payloads](06-payload-encrypted.md) — Outer envelope format
 - [Section 14: Cryptography](14-crypto.md) — Encrypt-then-MAC
-- Test vectors: [`corpus/payloads/path-return/`](https://github.com/swaits/meshcore-spec/tree/main/versions/v0.1.0/corpus/payloads/path-return/)
+- Test vectors: [`corpus/payloads/path-return/`](https://git.swaits.com/swaits/meshcore-spec/src/branch/main/versions/v0.1.0/corpus/payloads/path-return/)
 
 ### Reference Implementation