Track prompt cache write token usage (#33454)

## What changed

- Parse `cache_write_tokens` from response input token details and carry it through token usage aggregation.
- Expose `cache_write_input_tokens` in protocol, app-server, exec, and TypeScript SDK usage events, defaulting it to zero for compatibility with older payloads.
- Report cache-write usage in analytics, metrics, traces, and rollout data alongside existing cache-read usage.

## Testing

- Add coverage for response parsing, usage event output, aggregation, analytics, metrics, and telemetry fields.

GitOrigin-RevId: 634e4fbe3086a8923c0ee13b622573e7d9d221bd

codex-rs/app-server-protocol/schema/json/v2/ThreadTokenUsageUpdatedNotification.json

@@ -25,6 +25,11 @@
     },
     "TokenUsageBreakdown": {
       "properties": {
+        "cacheWriteInputTokens": {
+          "default": 0,
+          "format": "int64",
+          "type": "integer"
+        },
         "cachedInputTokens": {
           "format": "int64",
           "type": "integer"