test: add http2 handler e2e suite and tighten host-mapper + idle-timeout tests

Add tests/e2e/http2_test.go covering the http2 handler/listener/connector/dialer
end-to-end through the canonical gost-as-client pattern (8 subtests: forward,
auth, bypass, probeResist/metadata, h2 stream multiplexing). Include
testdata/http2/{server,server_auth,server_bypass,server_proberesist,client,
client_auth}.yaml. Note that h2/h2c listeners pair with the tunnel handler
and only http2 listener pairs with handler http2 (reads r/w from metadata).

Tighten TestDNSHostMapper by pointing the handler at an unreachable upstream
so unmapped names fail at the exchanger, confirming the host-mapper path was
the sole reason mapped names resolved. Fix http_idle_timeout.py to speak HTTP
through the CONNECT tunnel rather than a raw ping, matching the echo backend.

Co-Authored-By: Claude <noreply@anthropic.com>

tests/e2e/testdata/dns/server_hosts.yaml

@@ -4,7 +4,10 @@ services:
   handler:
     type: dns
     metadata:
-      # No upstream — host mapper resolves before exchanger is ever reached.
+      # Unreachable upstream so the system-DNS fallback is bypassed.
+      # The host mapper resolves mapped names before the exchanger is
+      # reached; unmapped names must hit the exchanger and fail.
+      dns: udp://127.0.0.1:1
       timeout: 2s
   listener:
     type: dns

tests/e2e/testdata/http2/client.yaml

@@ -0,0 +1,20 @@
+services:
+- name: http-proxy
+  addr: :8080
+  handler:
+    type: http
+    chain: h2-chain
+  listener:
+    type: tcp
+
+chains:
+- name: h2-chain
+  hops:
+  - name: hop-0
+    nodes:
+    - name: node-0
+      addr: {{.ServerAddr}}
+      connector:
+        type: http2
+      dialer:
+        type: http2

tests/e2e/testdata/http2/client_auth.yaml

@@ -0,0 +1,23 @@
+services:
+- name: http-proxy
+  addr: :8080
+  handler:
+    type: http
+    chain: h2-chain
+  listener:
+    type: tcp
+
+chains:
+- name: h2-chain
+  hops:
+  - name: hop-0
+    nodes:
+    - name: node-0
+      addr: {{.ServerAddr}}
+      connector:
+        type: http2
+        auth:
+          username: user
+          password: pass
+      dialer:
+        type: http2

tests/e2e/testdata/http2/server.yaml

@@ -0,0 +1,7 @@
+services:
+- name: h2-proxy
+  addr: :8443
+  handler:
+    type: http2
+  listener:
+    type: http2

tests/e2e/testdata/http2/server_auth.yaml

@@ -0,0 +1,18 @@
+services:
+- name: h2-proxy-auth
+  addr: :8443
+  handler:
+    type: http2
+    auther: auther-0
+    metadata:
+      # authBasicRealm: custom realm in 407 Proxy-Authenticate header
+      authBasicRealm: gost-e2e-realm
+      # hash: pin upstream selection by request host (metadata parse coverage)
+      hash: host
+  listener:
+    type: http2
+authers:
+- name: auther-0
+  auths:
+  - username: user
+    password: pass

tests/e2e/testdata/http2/server_bypass.yaml

@@ -0,0 +1,20 @@
+bypasses:
+- name: bypass-0
+  matchers:
+  - 0.0.0.0/0
+
+services:
+- name: h2-proxy-bypass
+  addr: :8443
+  handler:
+    type: http2
+    auther: auther-0
+  listener:
+    type: http2
+  bypass: bypass-0
+
+authers:
+- name: auther-0
+  auths:
+  - username: user
+    password: pass

tests/e2e/testdata/http2/server_proberesist.yaml

@@ -0,0 +1,20 @@
+services:
+- name: h2-proxy-pr
+  addr: :8443
+  handler:
+    type: http2
+    auther: auther-0
+    metadata:
+      # probeResist: hide the proxy behind a 404 decoy on auth failure
+      probeResist: code:404
+      # header: custom response headers set on proxy responses
+      header:
+        X-Proxy-Info: gost-e2e
+      authBasicRealm: gost-e2e-realm
+  listener:
+    type: http2
+authers:
+- name: auther-0
+  auths:
+  - username: user
+    password: pass