feat(providers): add Z.AI coding plan (global + China)

Providers 17-18 (20th & 21st registry variants), sourced authoritatively
from Pi (earendil-works/pi), the open-source agent whose provider list is
being mirrored. Pi's zai.ts / zai-coding-cn.ts use plain openAICompletionsApi
(NO special thinking dialect — overturns the matrix's 'thinking:{type} → new
dialect' concern), so Kigi maps them to Passthrough. Global: api.z.ai/api/
coding/paas/v4, ZAI_API_KEY, models.dev zai-coding-plan. China (Zhipu
BigModel): open.bigmodel.cn/api/coding/paas/v4, ZAI_CODING_CN_API_KEY,
models.dev zhipuai-coding-plan. Both Bearer + OpenAI listing + ChatCompletions
+ restrict_to_enriched; /models is auth-gated → validator.

id-match is PROVEN (not just assumed like Qwen): Pi's static model ids
[glm-4.5-air, glm-4.7, glm-5-turbo, glm-5.1, glm-5.2, glm-5v-turbo] are
byte-identical to the models.dev zai-coding-plan keys, all tool_call=true, so
restrict keeps every model with no silent-empty risk. Review found no defects.
GLM thinking is not lost (reasoning_content is parsed regardless of dialect).

Tests: e2e proves enrichment-supplied context + non-vacuous restrict (a
non-enriched wire model is dropped) + Passthrough; both variants' validation
tests hit /models and assert the per-variant console host (z.ai vs
open.bigmodel.cn). Registry at 21; picker 22 rows.

Also fixes the welcome login-picker test for the now-taller menu (renders at
a taller viewport to verify content coverage) and logs the real menu-overflow
UX debt: the picker clips rows past the fold with no scroll (q/l shortcuts
still work; only shown when unauthenticated) — deferred to its own cycle.

crates/codegen/kigi-shell/src/agent/models_fetch.rs

@@ -2260,6 +2260,94 @@ mod tests {
         assert_eq!(cfg.chat_compat, kigi_sampling_types::ChatCompat::Kimi);
     }
 
+    /// Z.AI-cycle e2e: OpenAI-compatible GLM coding plan (per Pi, plain
+    /// completions — no thinking dialect). /models is auth-gated + minimal, so
+    /// enrichment supplies context; restrict drops any wire model absent from
+    /// the models.dev "zai-coding-plan" snapshot; bare id round-trips under the
+    /// zai key; Passthrough dialect.
+    #[tokio::test(flavor = "multi_thread")]
+    #[serial_test::serial]
+    async fn zai_enriches_restricts_and_maps_passthrough() {
+        let platform_server = wiremock::MockServer::start().await;
+        wiremock::Mock::given(wiremock::matchers::method("GET"))
+            .and(wiremock::matchers::path("/models"))
+            .respond_with(wiremock::ResponseTemplate::new(200).set_body_json(
+                serde_json::json!({ "data": [
+                    { "id": "glm-5.2", "object": "model" },
+                    // not in the enrichment snapshot → dropped by restrict.
+                    { "id": "glm-experimental-unlisted", "object": "model" }
+                ]}),
+            ))
+            .expect(1)
+            .mount(&platform_server)
+            .await;
+        let modelsdev_server = wiremock::MockServer::start().await;
+        wiremock::Mock::given(wiremock::matchers::method("GET"))
+            .and(wiremock::matchers::path("/api.json"))
+            .respond_with(wiremock::ResponseTemplate::new(200).set_body_json(
+                serde_json::json!({ "zai-coding-plan": { "models": {
+                    "glm-5.2": {
+                        "limit": {"context": 200000, "output": 128000},
+                        "tool_call": true
+                    }
+                }}}),
+            ))
+            .expect(1)
+            .mount(&modelsdev_server)
+            .await;
+        let cache_dir = tempfile::tempdir().unwrap();
+        let _base =
+            kigi_test_support::EnvGuard::set(kigi_models::ZAI_BASE_URL_ENV, platform_server.uri());
+        let _mdev = kigi_test_support::EnvGuard::set(
+            crate::agent::enrichment_fetch::MODELS_DEV_URL_ENV,
+            format!("{}/api.json", modelsdev_server.uri()),
+        );
+        let _mdev_cache = kigi_test_support::EnvGuard::set(
+            crate::agent::enrichment_fetch::MODELS_DEV_CACHE_DIR_ENV,
+            cache_dir.path(),
+        );
+        let endpoints = crate::agent::config::EndpointsConfig::default();
+        let keys = crate::agent::models::PlatformApiKeys::test_single(
+            kigi_models::PlatformId::Zai,
+            "zai-1",
+        );
+        let result = tokio::task::spawn_blocking(move || {
+            fetch_platform_models_blocking(&endpoints, None, &keys)
+        })
+        .await
+        .unwrap()
+        .expect("fetch must succeed");
+        assert_eq!(
+            result
+                .models
+                .iter()
+                .map(|m| m.id.as_deref().unwrap_or_default())
+                .collect::<Vec<_>>(),
+            vec!["zai/glm-5.2"],
+            "the non-enriched wire model is dropped by restrict_to_enriched"
+        );
+        let entry = &result.models[0];
+        assert_eq!(
+            entry.context_window.get(),
+            200_000,
+            "context comes from enrichment (the wire listing carries none)"
+        );
+        assert_eq!(entry.max_completion_tokens, Some(128_000));
+        assert_eq!(entry.model, "glm-5.2");
+        let model_entry = crate::agent::config::ModelEntry::from_config_entry(entry);
+        let creds = crate::agent::config::ResolvedCredentials {
+            api_key: Some("zai-1".into()),
+            base_url: entry.base_url.clone(),
+            auth_type: kigi_chat_state::AuthType::ApiKey,
+            auth_scheme: Default::default(),
+        };
+        let cfg = crate::agent::config::sampling_config_for_model(&model_entry, creds, None);
+        assert_eq!(
+            cfg.chat_compat,
+            kigi_sampling_types::ChatCompat::Passthrough
+        );
+    }
+
     #[test]
     fn get_env_keys_parses_strings_and_rejects_non_strings() {
         use crate::agent::config::EnvKeys;