Add WatchEvents, enable/disable/weight RPCs, and config check

gRPC / proto
- Rename WatchBackendEvents → WatchEvents; return a stream of Event
  oneof (LogEvent, BackendEvent, FrontendEvent) with optional filter
  flags (log, log_level, backend, frontend)
- Add EnableBackend, DisableBackend, SetFrontendPoolBackendWeight RPCs
- Rename PauseResumeRequest → BackendRequest
- Add CheckConfig RPC returning ok/parse_error/semantic_error

maglevd
- Route slog through a LogBroadcaster (slog.Handler) so WatchEvents
  subscribers can receive structured log records independently of the
  daemon's own --log-level
- Add --reflection flag (default true) to toggle gRPC server reflection
- Add --check flag: validates config file and exits 0/1/2
- SIGHUP: use config.Check before applying reload; log parse vs semantic
  error separately; refuse reload on any error
- Rename default config path /etc/maglev → /etc/vpp-maglev

maglevc
- Add 'watch events [num <n>] [log [level <level>]] [backend] [frontend]'
  command; prints compact protojson, stops on any keypress or Ctrl-C;
  uses cbreak mode (not raw) so output post-processing is preserved
- Add 'set backend <name> enable|disable'
- Add 'set frontend <name> pool <pool> backend <name> weight <0-100>'
- Add 'config check' command

Debian packaging
- Rename service unit to vpp-maglevd.service
- Rename conffiles to /etc/default/vpp-maglev and /etc/vpp-maglev/
- Create maglevd system user/group in postinst; add to vpp group if present
- Add postrm; add adduser to Depends

docs/maglevd.8

@@ -6,6 +6,7 @@ maglevd \- Maglev health\-checker daemon
 [\fB\-config\fR \fIfile\fR]
 [\fB\-grpc\-addr\fR \fIaddr\fR]
 [\fB\-log\-level\fR \fIlevel\fR]
+[\fB\-reflection\fR[=\fIbool\fR]]
 [\fB\-version\fR]
 .SH DESCRIPTION
 .B maglevd
@@ -32,7 +33,7 @@ parentheses); the flag takes precedence.
 .TP
 .BI \-config " file"
 Path to the YAML configuration file.
-.RI "(default: " /etc/maglev/maglev.conf "; env: " MAGLEV_CONFIG )
+.RI "(default: " /etc/vpp-maglev/maglev.yaml "; env: " MAGLEV_CONFIG )
 .TP
 .BI \-grpc\-addr " addr"
 TCP address on which the gRPC server listens.
@@ -47,6 +48,16 @@ or
 .BR error .
 .RI "(default: " info "; env: " MAGLEV_LOG_LEVEL )
 .TP
+.B \-reflection
+Enable gRPC server reflection so that clients such as
+.BR grpcurl (1)
+can introspect the API without access to the
+.I .proto
+file.
+Enabled by default; pass
+.B \-reflection=false
+to disable.
+.TP
 .B \-version
 Print version, commit hash, and build date, then exit.
 .SH SIGNALS
@@ -60,10 +71,10 @@ backend workers are left running.
 Gracefully shut down: drain active gRPC streams, then exit.
 .SH FILES
 .TP
-.I /etc/maglev/maglev.conf
+.I /etc/vpp-maglev/maglev.yaml
 Default configuration file (YAML).
 .TP
-.I /etc/default/maglev
+.I /etc/default/vpp-maglev
 Environment file sourced by the systemd unit before starting
 .BR maglevd .
 .SH CONFIGURATION
@@ -77,7 +88,7 @@ and
 .BR frontends .
 .PP
 See the example at
-.I /etc/maglev/maglev.conf
+.I /etc/vpp-maglev/maglev.yaml
 and the full reference in the project documentation.
 .SH SEE ALSO
 .BR maglevc (1)