Issue 17774 - Usage - Local - Show data from midnight to midnight of selected dates for browser time zone (AI assisted) (openclaw#19357) thanks @huntharo

Verified:
- pnpm install --frozen-lockfile
- pnpm build
- pnpm check
- pnpm test:macmini (override approved by Tak for this run; local baseline failures outside PR scope)

Co-authored-by: huntharo <5617868+huntharo@users.noreply.github.com>
Co-authored-by: Tak Hoffman <781889+Takhoffman@users.noreply.github.com>

src/gateway/protocol/schema/sessions.ts

@@ -114,6 +114,12 @@ export const SessionsUsageParamsSchema = Type.Object(
     startDate: Type.Optional(Type.String({ pattern: "^\\d{4}-\\d{2}-\\d{2}$" })),
     /** End date for range filter (YYYY-MM-DD). */
     endDate: Type.Optional(Type.String({ pattern: "^\\d{4}-\\d{2}-\\d{2}$" })),
+    /** How start/end dates should be interpreted. Defaults to UTC when omitted. */
+    mode: Type.Optional(
+      Type.Union([Type.Literal("utc"), Type.Literal("gateway"), Type.Literal("specific")]),
+    ),
+    /** UTC offset to use when mode is `specific` (for example, UTC-4 or UTC+5:30). */
+    utcOffset: Type.Optional(Type.String({ pattern: "^UTC[+-]\\d{1,2}(?::[0-5]\\d)?$" })),
     /** Maximum sessions to return (default 50). */
     limit: Type.Optional(Type.Integer({ minimum: 1 })),
     /** Include context weight breakdown (systemPromptReport). */