chore: update Claude 4.6 context window to 1M (GA)

Claude Opus 4.6 and Sonnet 4.6 1M context window is now GA and no
longer requires a beta header. Update contextWindow from 200k to 1M
for all OpenClaw/OpenCode presets (27 entries in OpenClaw, 1 in
OpenCode Bedrock). Also add claude-sonnet-4-6 model pricing seed.

src-tauri/src/database/schema.rs

@@ -1059,6 +1059,14 @@ impl Database {
                 "0.50",
                 "6.25",
             ),
+            (
+                "claude-sonnet-4-6-20260217",
+                "Claude Sonnet 4.6",
+                "3",
+                "15",
+                "0.30",
+                "3.75",
+            ),
             // Claude 4.5 系列
             (
                 "claude-opus-4-5-20251101",