chore: point MSD at git.golem15.com/golem15/msd-core

The fork lives on the golem15 Gitea forge, not GitHub. Package identity now
parses either host and derives in-place raw URLs for Gitea; the identity-drift
lint accepts the new host; README drops GitHub-only badges and the npm
quickstart in favour of the checkout installer.

CONTRIBUTING.md

@@ -4,7 +4,7 @@
 
 ```bash
 # Clone the repo
-git clone https://github.com/golem15com/msd-core.git
+git clone https://git.golem15.com/golem15/msd-core.git
 cd msd-core
 
 # Activate the pinned Node version from .nvmrc
@@ -142,7 +142,7 @@ git checkout next
 git pull --ff-only origin next
 git checkout -b fix/3187-config-corruption
 # ... commit, push
-gh pr create --base next --repo golem15com/msd-core
+gh pr create --base next --repo golem15/msd-core
 ```
 
 If you target the wrong branch by accident, the `PR Target Validator`
@@ -155,7 +155,7 @@ another PR to `next` lands — so in practice you rebase much less.
 
 **But `next` does still require "up-to-date before merging".** Branch
 protection has `required_status_checks.strict = true`; check it yourself with
-`gh api repos/golem15com/msd-core/branches/next/protection --jq '.required_status_checks.strict'`.
+`gh api repos/golem15/msd-core/branches/next/protection --jq '.required_status_checks.strict'`.
 If another PR lands while yours is open, yours goes `BEHIND` and must be
 rebased before it can merge.
 
@@ -238,7 +238,7 @@ To re-format an existing release by hand (e.g. backfilling an older release):
 
 ```bash
 node scripts/release-notes/format-github-release-notes.cjs \
-  --tag vX.Y.Z --repo golem15com/msd-core --apply
+  --tag vX.Y.Z --repo golem15/msd-core --apply
 ```
 
 Omit `--apply` to print the reformatted body to stdout for review without