fix(coraza-spoe): match upstream's required spoe shape (groups, arg order, names)

Three real bugs in the SPOE config caught when HAProxy validated the
generated file:

1. spoe-agent must declare `groups` not `messages`. The `messages` form
   doesn't make the message reachable via `send-spoe-group`; HAProxy
   complained:
     unable to find SPOE group 'coraza-check' into SPOE engine 'coraza'

2. send-spoe-group references a spoe-GROUP name, which needs its own
   block. Added `spoe-group coraza-req { messages coraza-req }` as
   the indirection layer.

3. Arg names + ORDER are required to match what Coraza-SPOA parses
   positionally. My version had `dest-ip`/`dest-port`; upstream's
   example/haproxy/coraza.cfg (v0.7.1) uses `dst-ip`/`dst-port`.
   Renamed and reordered to match upstream verbatim, including the
   `app=str(haproxy)` literal that matches our config.yaml application
   name.

Also corrected misleading comment about `set-on-error continue`: that
option actually sets a variable on error; the fail-open behavior comes
from us deliberately NOT adding a `http-request deny if errored` rule
in the frontend. Renamed the variable to `error` (matching upstream)
and updated comments to be accurate.

Listener template's send-spoe-group action updated to reference the
new group name `coraza-req`.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

templates/hap_coraza_spoe_engine.tpl

@@ -5,25 +5,33 @@
 # via `filter spoe engine coraza config /etc/haproxy/coraza-spoe.cfg`.
 #
 # Engine name "coraza" must match the engine name in the filter line in the
-# main config and the application name "haproxy" must match the application
-# block name in coraza-spoa's config.yaml.
+# main config; group name "coraza-req" must match the send-spoe-group action.
+# Application name "haproxy" must match the application block in coraza-spoa's
+# config.yaml.
+#
+# Reference: this config follows the shape from coraza-spoa's upstream
+# example/haproxy/coraza.cfg (v0.7.1). Arg names + ordering are required by
+# Coraza-SPOA exactly as specified — DO NOT reorder or rename without
+# coordinating with the agent.
 
 [coraza]
 
 spoe-agent coraza
-    # The single message we send (defined below) — per-request inspection.
-    messages    coraza-check
+    # `groups` (not `messages`) lists the spoe-group names this engine offers
+    # via `send-spoe-group` actions. The same group name appears below in a
+    # spoe-group block, which in turn references the actual message.
+    groups      coraza-req
 
-    # Prefix for any variables the agent sets back on the request.
+    # Prefix for variables the agent sets back on the request transaction —
+    # e.g. var(txn.coraza.error) when set-on-error triggers.
     option      var-prefix coraza
 
-    # FAIL-OPEN. If the SPOA is unreachable or times out, requests flow
-    # through uninspected rather than failing. For a hosting platform,
-    # availability beats unconditional inspection coverage.
-    option      set-on-error continue
+    # On agent error/timeout, set var(txn.coraza.error). We DON'T add a
+    # corresponding `http-request deny if { var(txn.coraza.error) -m bool }`
+    # in the frontend, so the request continues uninspected. This is the
+    # fail-open posture: WAF outage shouldn't 503 customer traffic.
+    option      set-on-error error
 
-    # Aggressive timeouts: we don't want the WAF to materially slow page
-    # loads. processing 100ms is the per-request inspection budget.
     timeout     hello       2s
     timeout     idle        2m
     timeout     processing  100ms
@@ -31,12 +39,16 @@ spoe-agent coraza
     use-backend coraza-spoa-backend
     log         global
 
-spoe-message coraza-check
-    # Send the request shape to Coraza for inspection.
-    # `app=str(haproxy)` matches the application named "haproxy" in
-    # coraza-spoa's config.yaml — that's how Coraza picks which ruleset
-    # to apply.
-    # NOTE: args must be on ONE line. HAProxy does not support backslash
-    # line continuations in spoe configs (verified the hard way 2026-05-12).
-    args app=str(haproxy) src-ip=src src-port=src_port dest-ip=dst dest-port=dst_port method=method path=path query=query version=req.ver headers=req.hdrs body=req.body
-    event on-frontend-http-request
+# Per-request inspection message. No `event` directive — fires only when
+# explicitly invoked from haproxy.cfg via `http-request send-spoe-group`.
+# Arg order/names are mandatory: Coraza-SPOA parses positionally and renames
+# break the agent. `app=str(haproxy)` is the literal application name from
+# coraza-spoa's config.yaml `applications:` block.
+spoe-message coraza-req
+    args app=str(haproxy) src-ip=src src-port=src_port dst-ip=dst dst-port=dst_port method=method path=path query=query version=req.ver headers=req.hdrs body=req.body
+
+# Group binding for send-spoe-group invocation in the frontend. One group,
+# one message; could add more in the future (e.g. coraza-res for response
+# inspection — currently disabled in coraza-spoa's config.yaml).
+spoe-group coraza-req
+    messages coraza-req