Add totalTokens field to Usage type

- Added totalTokens field to Usage interface in pi-ai
- Anthropic: computed as input + output + cacheRead + cacheWrite
- OpenAI/Google: uses native total_tokens/totalTokenCount
- Fixed openai-completions to compute totalTokens when reasoning tokens present
- Updated calculateContextTokens() to use totalTokens field
- Added comprehensive test covering 13 providers

fixes #130

packages/web-ui/src/storage/stores/sessions-store.ts

@@ -101,6 +101,7 @@ export class SessionsStore extends Store {
 				output: 0,
 				cacheRead: 0,
 				cacheWrite: 0,
+				totalTokens: 0,
 				cost: { input: 0, output: 0, cacheRead: 0, cacheWrite: 0, total: 0 },
 			},
 			thinkingLevel: state.thinkingLevel || "off",

packages/web-ui/src/storage/types.ts

@@ -118,6 +118,8 @@ export interface SessionMetadata {
 		cacheRead: number;
 		/** Total cache write tokens */
 		cacheWrite: number;
+		/** Total tokens processed */
+		totalTokens: number;
 		/** Total cost breakdown */
 		cost: {
 			input: number;