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.

docs/maglevc.1

@@ -0,0 +1,112 @@
+.TH MAGLEVC 1 "April 2026" "vpp\-maglev" "User Commands"
+.SH NAME
+maglevc \- Maglev health\-checker CLI client
+.SH SYNOPSIS
+.B maglevc
+[\fB\-server\fR \fIaddr\fR]
+[\fB\-color\fR[=\fIbool\fR]]
+[\fIcommand\fR [\fIargs\fR...]]
+.SH DESCRIPTION
+.B maglevc
+is an interactive CLI client for
+.BR maglevd (8).
+Without arguments it opens a readline shell with tab completion and
+inline help.
+A command may also be passed directly on the command line for one\-shot use,
+which is useful for scripting (use
+.B \-color=false
+to suppress ANSI codes).
+.PP
+When the shell starts it prints the build version and connects to the
+.B maglevd
+gRPC server specified by
+.BR \-server .
+.SH OPTIONS
+.TP
+.BI \-server " addr"
+Address of the
+.B maglevd
+gRPC server.
+(default:
+.IR localhost:9090 )
+.TP
+.BR \-color [=\fIbool\fR]
+Colorize static field labels in output using ANSI dark blue.
+(default: true)
+Pass
+.B \-color=false
+to disable, e.g.\& when piping output.
+.SH COMMANDS
+Commands are entered at the
+.B maglevc>
+prompt or passed as arguments on the command line.
+All static tokens support tab completion; dynamic names (frontend, backend,
+health\-check names) are completed by querying the server.
+Type
+.B ?
+at any point to list completions without advancing the input.
+.SS Show commands
+.TP
+.B show version
+Print build version, commit hash, and build date.
+.TP
+.B show frontends
+List all configured frontends.
+.TP
+.BI "show frontend " name
+Show address, protocol, port, description, and pools (with weights and
+disabled\-backend notation) for the named frontend.
+.TP
+.B show backends
+List all active backends.
+.TP
+.BI "show backend " name
+Show address, current health state (with duration), enabled flag,
+health\-check name, and recent state transitions with timestamps.
+.TP
+.B show healthchecks
+List all configured health checks.
+.TP
+.BI "show healthcheck " name
+Show the full configuration of the named health check.
+.SS Set commands
+.TP
+.BI "set backend " "name " pause
+Pause health checking for a backend, freezing its state.
+.TP
+.BI "set backend " "name " resume
+Resume health checking for a backend; state resets to
+.BR unknown .
+.SS Shell commands
+.TP
+.BR quit ", " exit
+Exit the interactive shell.
+.SH COMPLETION
+In interactive mode, press
+.B Tab
+to complete the current token.
+If more than one completion is possible, all candidates are listed.
+Type
+.B ?
+anywhere on the line to list candidates at that position without consuming
+the character or advancing the cursor.
+.SH EXAMPLES
+One\-shot query (no color, suitable for scripts):
+.PP
+.RS
+.EX
+maglevc \-color=false show backends
+.EE
+.RE
+.PP
+Interactive session:
+.PP
+.RS
+.EX
+maglevc \-server 10.0.0.1:9090
+.EE
+.RE
+.SH SEE ALSO
+.BR maglevd (8)
+.SH AUTHOR
+Pim van Pelt <pim@ipng.ch>