feat(pricing): add display pricing for Qwen 3.8 Flash and GLM 5.3 Flash

Qwen/Qwen3.8-Flash lists $0.16 input, $0.47 output, and $0.016 cache read
per million tokens, and z-ai/glm-5.3-flash lists $0.15, $0.50, and $0.03;
the official pricing page documents no cache-write rate for either model.

tests/test-pricing.ts

@@ -144,6 +144,18 @@ describe("MODEL_COSTS pricing overlay", () => {
       cacheRead: 0.04,
       cacheWrite: 0,
     })
+    assertCost("Qwen/Qwen3.8-Flash", {
+      input: 0.16,
+      output: 0.47,
+      cacheRead: 0.016,
+      cacheWrite: 0,
+    })
+    assertCost("z-ai/glm-5.3-flash", {
+      input: 0.15,
+      output: 0.5,
+      cacheRead: 0.03,
+      cacheWrite: 0,
+    })
     assertCost("google/gemini-3.7-flash", {
       input: 0.75,
       output: 3.75,