feat(server): present Silo identity and close the inherited upstream services

Two coupled changes that must land together, because the same files carry both:
the server now identifies itself as Silo, and every path that would have called
home to a MinIO-operated service is closed.

Product identity
- build-constants.go: store name, UA name and startup banner become Silo. The
  Go identifiers (MinioStoreName, MinioBannerName, ...) keep their names on
  purpose - renaming exported symbols would churn the compatibility surface for
  a cosmetic gain, and the rebrand guard freezes that surface.
- main.go, server-startup-msg.go, ftp-server.go and the user-visible log, help
  and error strings across cmd/ and internal/ switch to Silo. Original MinIO
  copyright, LICENSE, NOTICE and CREDITS are untouched; --version now prints
  the upstream copyright, the pgsty modification notice, and the trademark
  policy's approved "based on MinIO technology" attribution.
- api-headers.go: the HTTP Server header becomes "Silo". This is the one
  externally observable identity change, so TestCommonHeadersUseSiloProductName
  pins it - probes that sniff for "MinIO" must move to capability detection.
- Prometheus metric HELP strings keep their MinIO wording. They are part of the
  metrics contract the guard protects, not product copy.

Configuration directory
- config-dir.go: new installs use ~/.silo. If only ~/.minio exists it is still
  read, with a one-time notice and no files moved. If both exist ~/.silo wins
  and an ambiguity warning is emitted; an explicit --config-dir always wins.
  Covered by TestSelectDefaultConfigDir. The internal .minio.sys layout is
  never renamed - this rule applies to the user config directory only.

Upstream service lockdown
- globalInplaceUpdateDisabled is now true at initialization rather than being
  set from MINIO_UPDATE. common-main.go still parses MINIO_UPDATE so upgrading
  nodes do not fail on an unknown key, but warns that the value is ignored;
  there is no way to re-enable the updater. TestInplaceUpdateCannotBeEnabled
  guards that. Without this, an admin with mc could have overwritten
  /usr/bin/silo with an upstream MinIO binary.
- verifyBinary and commitBinary refuse early; the ServerUpdate v1/v2 admin
  routes and the peer-rest update endpoints stay registered and keep returning
  the existing programmatic error, so clients see a stable failure rather than
  a 404.
- MinioReleaseBaseURL and defaultMinisignPubkey are emptied: no dl.min.io
  download root, and upstream's minisign key is no longer a trust root for
  anything this fork ships.
- cmd/callhome.go is deleted and internal/config/subnet/ is reduced to parsing
  its old keys and reporting that the integration is disabled. config-current.go
  warns instead of failing when callhome or SUBNET settings are present, so an
  upgraded node with those keys still starts.
- internal/config/errors.go replaces the MinIO Slack and support entry points
  with Silo documentation and issue links. Error codes and programmatic fields
  are unchanged.

Verified: the compatibility baseline is unchanged except for the deliberate
removal of the /api/health/upload SUBNET route; go build, go vet and the full
cmd/ and internal/ unit suites pass; a locally built binary starts, serves
S3/Admin/metrics on the unchanged /minio/* routes, answers with Server: Silo,
and falls back to a pre-existing ~/.minio with the expected notice.

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

internal/config/errors.go

@@ -21,8 +21,8 @@ package config
 var (
 	ErrInvalidXLValue = newErrFn(
 		"Invalid drive path",
-		"Please provide a fresh drive for single drive MinIO setup",
-		"MinIO only supports fresh drive paths",
+		"Please provide a fresh drive for a single-drive Silo setup",
+		"Silo only supports fresh drive paths",
 	)
 
 	ErrInvalidBrowserValue = newErrFn(
@@ -118,14 +118,14 @@ var (
 	ErrStorageClassValue = newErrFn(
 		"Invalid storage class value",
 		"Please check the value",
-		`MINIO_STORAGE_CLASS_STANDARD: Format "EC:<Default_Parity_Standard_Class>" (e.g. "EC:3"). This sets the number of parity drives for MinIO server in Standard mode. Objects are stored in Standard mode, if storage class is not defined in Put request
-MINIO_STORAGE_CLASS_RRS: Format "EC:<Default_Parity_Reduced_Redundancy_Class>" (e.g. "EC:3"). This sets the number of parity drives for MinIO server in Reduced Redundancy mode. Objects are stored in Reduced Redundancy mode, if Put request specifies RRS storage class
-Refer to the link https://github.com/minio/minio/tree/master/docs/erasure/storage-class for more information`,
+		`MINIO_STORAGE_CLASS_STANDARD: Format "EC:<Default_Parity_Standard_Class>" (e.g. "EC:3"). This sets the number of parity drives for Silo in Standard mode. Objects are stored in Standard mode if no storage class is defined in the Put request.
+MINIO_STORAGE_CLASS_RRS: Format "EC:<Default_Parity_Reduced_Redundancy_Class>" (e.g. "EC:3"). This sets the number of parity drives for Silo in Reduced Redundancy mode. Objects are stored in Reduced Redundancy mode if the Put request specifies the RRS storage class.
+See https://silo.pgsty.com/operations/concepts/erasure-coding/ for more information.`,
 	)
 
 	ErrUnexpectedBackendVersion = newErrFn(
 		"Backend version seems to be too recent",
-		"Please update to the latest MinIO version",
+		"Please update to the latest Silo version",
 		"",
 	)
 
@@ -143,8 +143,8 @@ Refer to the link https://github.com/minio/minio/tree/master/docs/erasure/storag
 		"Please check the endpoint",
 		`Single-Node modes requires absolute path without hostnames:
 Examples:
-   $ minio server /data/minio/ #Single Node Single Drive
-   $ minio server /data-{1...4}/minio # Single Node Multi Drive`,
+   $ silo server /data/silo/ # Single Node Single Drive
+   $ silo server /data-{1...4}/silo # Single Node Multi Drive`,
 	)
 
 	ErrUnsupportedBackend = newErrFn(
@@ -155,8 +155,8 @@ Examples:
 
 	ErrUnableToWriteInBackend = newErrFn(
 		"Unable to write to the backend",
-		"Please ensure MinIO binary has write permissions for the backend",
-		`Verify if MinIO binary is running as the same user who has write permissions for the backend`,
+		"Please ensure the Silo binary has write permissions for the backend",
+		`Verify that the Silo binary is running as the same user who has write permissions for the backend`,
 	)
 
 	ErrPortAlreadyInUse = newErrFn(
@@ -167,8 +167,8 @@ Examples:
 
 	ErrPortAccess = newErrFn(
 		"Unable to use specified port",
-		"Please ensure MinIO binary has 'cap_net_bind_service=+ep' permissions",
-		`Use 'sudo setcap cap_net_bind_service=+ep /path/to/minio' to provide sufficient permissions`,
+		"Please ensure the Silo binary has 'cap_net_bind_service=+ep' permissions",
+		`Use 'sudo setcap cap_net_bind_service=+ep /path/to/silo' to provide sufficient permissions`,
 	)
 
 	ErrTLSReadError = newErrFn(
@@ -209,7 +209,7 @@ Examples:
 
 	ErrUnexpectedError = newErrFn(
 		"Unexpected error",
-		"Please contact MinIO at https://slack.min.io",
+		"Please report this Silo error at https://github.com/pgsty/minio/issues",
 		"",
 	)