Pools, CLI, versioning, Debian packaging, HTTPS fix

- Replaced flat `backends: [...]` list on frontends with an ordered `pools:`
  list; each pool has a name and a map of backends with per-pool weights (0–100,
  default 100). Pools express priority: first pool with a healthy backend wins.
- Removed global backend weight (was on the backend, now lives in the pool).
- Config validation enforces non-empty pools, non-empty pool names, weight
  range, and consistent address families across all pools of a frontend.

- Added `PoolBackendInfo { name, weight }` and changed `PoolInfo.backends` from
  `repeated string` to `repeated PoolBackendInfo` so weights are visible over
  the API.

- Full interactive shell with readline, tab completion, and `?` inline help.
- Command tree parser (Walk) handles fixed keywords and dynamic slot nodes;
  prefix matching with exact-match priority.
- Commands: `show version/frontends/frontend/backends/backend/healthchecks/
  healthcheck`, `set backend <name> pause|resume`, `quit`/`exit`.
- `show frontend` output is hierarchical (pools → backends) with per-backend
  weights and `[disabled]` notation; pool section uses fixed-width formatting
  so ANSI color codes don't corrupt tabwriter alignment.
- `-color` flag (default true) wraps static field labels in dark-blue ANSI;
  works correctly with tabwriter because all labels carry identical-length
  escape sequences.

- `cmd/version.go` package holds `version`, `commit`, `date` vars set at build
  time via `-ldflags -X`.
- `make build` / `make build-amd64` / `make build-arm64` all inject
  `VERSION=0.1.1`, `COMMIT_HASH` (from `git rev-parse --short HEAD`), and
  `DATE` (UTC ISO-8601).
- `maglevc` prints version on interactive startup and exposes `show version`.
- `maglevd` logs version/commit/date at startup; `-version` flag prints and exits.

- `doHTTPProbe` was building a `https://` target URL even though TLS was already
  applied to the connection inside `inNetns`. `http.Transport` then wrapped the
  connection in a second TLS layer, producing "http: server gave HTTP response
  to HTTPS client". Fixed by always using `http://` in the target URL.
- Added `TestHTTPSProbe` using `httptest.NewTLSServer` to cover the full path.

- New `docs/user-guide.md`: maglevd flags/signals, maglevc commands, shell
  completion, and command-tree parser walkthrough.
- New `docs/healthchecks.md`: state machine, rise/fall model, probe intervals,
  all transition events with log examples.
- Updated `docs/config-guide.md`: pools design, removed global weight from
  backends, updated all examples.
- Updated `README.md`: packaging table, build paths, corrected binary locations
  (`/usr/sbin/maglevd`), config filename (`.yaml`).

- `debian/` directory contains `control.in`, `maglevd.service`, `default.maglev`,
  `maglev.yaml` (example config), `conffiles`, `postinst`, `prerm`.
- `debian/build-deb.sh` stages a package tree and calls `dpkg-deb`; emits
  `build/vpp-maglev_<version>~<commit>_<arch>.deb`.
- Cross-compiles for amd64 and arm64 in one `make pkg-deb` invocation.
- `maglevd` installed to `/usr/sbin/`, `maglevc` to `/usr/bin/`.
- Service reads `MAGLEV_CONFIG` from `/etc/default/maglev`
  (default: `/etc/maglev/maglev.yaml`).
- Man pages `maglevd(8)` and `maglevc(1)` live in `docs/` and are gzip'd into
  the package.
- All build output goes to `build/<arch>/`; `build/` is gitignored.

README.md

@@ -5,29 +5,58 @@ Health checker and gRPC control plane for VPP Maglev load balancing.
 ## Build
 
 ```sh
-make          # builds bin/maglevd
+make          # builds build/<arch>/maglevd and build/<arch>/maglevc
 make test     # runs all tests
 make proto    # regenerates gRPC stubs from proto/maglev.proto
+make lint     # runs golangci-lint
 ```
 
-Requires Go 1.25+ and (for `make proto`) `protoc` with `protoc-gen-go` and `protoc-gen-go-grpc`.
+Requires Go 1.25+ and (for `make proto`) `protoc` with `protoc-gen-go` and
+`protoc-gen-go-grpc`.
+
+## Debian package
+
+```sh
+make pkg-deb
+```
+
+Produces `vpp-maglev_<version>_amd64.deb` and `vpp-maglev_<version>_arm64.deb`
+in the project root by cross-compiling with `GOOS=linux GOARCH=<arch>`.
+Requires `dpkg-deb` (available on any Debian/Ubuntu host).
+
+The package installs:
+
+| Path | Content |
+|---|---|
+| `/usr/sbin/maglevd` | Health-checker daemon |
+| `/usr/bin/maglevc` | Interactive CLI client |
+| `/lib/systemd/system/maglevd.service` | systemd unit |
+| `/etc/default/maglev` | Environment file for the unit (conffile) |
+| `/etc/maglev/maglev.yaml` | Example configuration file (conffile) |
+| `/usr/share/man/man8/maglevd.8.gz` | Man page |
+| `/usr/share/man/man1/maglevc.1.gz` | Man page |
+
+After installing, the unit is enabled but not started automatically:
+
+```sh
+# edit /etc/maglev/maglev.yaml, then:
+systemctl start maglevd
+```
 
 ## Run
 
 ```sh
 maglevd --config /etc/maglev/maglev.yaml --grpc-addr :9090
+maglevd --version                        # print version and exit
+
+maglevc --server localhost:9090          # interactive shell
+maglevc show backend nginx0-ams          # one-shot
+maglevc -color=false show backends       # one-shot, no ANSI color
+maglevc set backend nginx0-ams pause
 ```
 
-| Flag | Env | Default |
-|---|---|---|
-| `--config` | `MAGLEV_CONFIG` | `/etc/maglev/frontend.yaml` |
-| `--grpc-addr` | `MAGLEV_GRPC_ADDR` | `:9090` |
-| `--log-level` | `MAGLEV_LOG_LEVEL` | `info` |
-
-Send `SIGHUP` to reload the config without restarting. Backends whose health-check config is
-unchanged continue probing uninterrupted.
-
-`maglevd` requires `CAP_NET_RAW` to open raw ICMP sockets.
+Send `SIGHUP` to `maglevd` to reload config without restarting.
+`maglevd` requires `CAP_NET_RAW` for ICMP health checks.
 
 ## Minimal config
 
@@ -51,10 +80,16 @@ maglev:
       address: 192.0.2.1
       protocol: tcp
       port: 80
-      backends: [web0, web1]
+      pools:
+        - name: primary
+          backends:
+            web0: {}
+            web1: {}
 ```
 
+See [docs/user-guide.md](docs/user-guide.md) for flags, signals, and `maglevc` usage.
 See [docs/config-guide.md](docs/config-guide.md) for the full configuration reference.
+See [docs/healthchecks.md](docs/healthchecks.md) for health state machine details.
 
 ## Docker