chore: cut over to pgsty/silo and main

The transitional references land in one commit, because they are only correct
together: the repository is pgsty/silo, its default branch is main, and nothing
in the tree should point a user at the old names.

Changed:

- Workflow branch filters. go.yml and vulncheck.yml gated on `branches: master`
  for both push and pull_request, so renaming the default branch would have
  taken automatic CI offline with no error and no signal - the workflows would
  simply never trigger again. They now name main.
- Release target. goreleaser's `release.github.name` becomes silo, which is
  what actually decides where a tagged build publishes. sign-release-rpms.sh's
  GH_REPO default follows.
- The OCI `image.source` label, the Helm chart `sources` entry, the security
  advisory link in the issue-template config, and the go.mod comment citing the
  LDAP TLS fix.
- 115 occurrences across README, README_ZH, SECURITY, CONTRIBUTING and 30 docs
  pages, including 72 links that also carried the master branch in their path.
  Those matter most: GitHub redirects clone, fetch, push and web URLs after a
  rename, but raw.githubusercontent.com does not, and neither follows a branch
  rename - every one of those links would 404 twice over.
- Three error strings in cmd/erasure-sets.go, cmd/storage-errors.go and
  internal/config/errors.go that print an issue URL to operators. These are Go
  string literals inside rebrand-guard's brand allowlist, so the baseline is
  regenerated. The regeneration removes exactly those three entries and adds
  none; all twelve other protected sets, including the 9014 exported symbols,
  are byte-identical.
- The transitional-naming disclaimers in README, README_ZH, SECURITY and
  CONTRIBUTING are dropped, since they no longer describe anything.

Deliberately unchanged, all three because they exist to reject or freeze the old
name rather than to point at it:

- buildscripts/minio-upgrade.sh pins pgsty/minio@sha256:b6bfe72... - the frozen
  pre-rebrand image is the control group for the MinIO-to-Silo upgrade test.
- helm-migration-guard rejects any rendered container still pulling pgsty/minio.
- verify-rebrand.sh rejects the same in the delivery surfaces.

Also unchanged: docs/config/README.md links to pgsty/mc/blob/master, and that
repository's default branch really is still master. It moves when mc does.

verify-rebrand.sh gains three assertions so this cannot silently regress: no
source reference may name pgsty/minio outside the three allowlisted guards, no
link may target pgsty/silo's master branch, and go.yml and vulncheck.yml must
filter on main. Both new rejections were negative-tested - reintroducing a
master branch filter and adding a pgsty/minio URL each fail the gate with the
specific message.

This commit assumes the rename actually happens. Until the GitHub branch and
repository renames are executed, the links it introduces do not resolve.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>

docs/kms/IAM.md

@@ -7,7 +7,7 @@ Silo supports encrypting config, IAM assets with KMS provided keys. If the KMS i
 Silo supports two ways of encrypting IAM and configuration data.
 You can either use KES - together with an external KMS - or, much simpler,
 set the env. variable `MINIO_KMS_SECRET_KEY` and start/restart the Silo server. For more details about KES and how
-to set it up refer to our [KMS Guide](https://github.com/pgsty/minio/blob/master/docs/kms/README.md).
+to set it up refer to our [KMS Guide](https://github.com/pgsty/silo/blob/main/docs/kms/README.md).
 
 Instead of configuring an external KMS you can start with a single key by
 setting the env. variable `MINIO_KMS_SECRET_KEY`. It expects the following
@@ -45,7 +45,7 @@ kes key create my-minio-key OSMM+vkKUTCvQs9YL/CVMIMt43HFhkUpqJxTmGl6rYw=
 
 - For instructions on setting up KES, see the [KES Getting Started guide](https://github.com/minio/kes/wiki/Getting-Started)
 
-- For instructions on using KES for encrypting the Silo backend, follow the [KMS Quick Start](https://github.com/pgsty/minio/tree/master/docs/kms). The SSE-S3 configuration setup also supports Silo KMS backend encryption.
+- For instructions on using KES for encrypting the Silo backend, follow the [KMS Quick Start](https://github.com/pgsty/silo/tree/main/docs/kms). The SSE-S3 configuration setup also supports Silo KMS backend encryption.
 
 ## FAQ