Web UI: add token usage dashboard (#10072)

* feat(ui): Token Usage dashboard with session analytics

Adds a comprehensive Token Usage view to the dashboard:

Backend:
- Extended session-cost-usage.ts with per-session daily breakdown
- Added date range filtering (startMs/endMs) to API endpoints
- New sessions.usage, sessions.usage.timeseries, sessions.usage.logs endpoints
- Cost breakdown by token type (input/output/cache read/write)

Frontend:
- Two-column layout: Daily chart + breakdown | Sessions list
- Interactive daily bar chart with click-to-filter and shift-click range select
- Session detail panel with usage timeline, conversation logs, context weight
- Filter chips for active day/session selections
- Toggle between tokens/cost view modes (default: cost)
- Responsive design for smaller screens

UX improvements:
- 21-day default date range
- Debounced date input (400ms)
- Session list shows filtered totals when days selected
- Context weight breakdown shows skills, tools, files contribution

* fix(ui): restore gatewayUrl validation and syncUrlWithSessionKey signature

- Restore normalizeGatewayUrl() to validate ws:/wss: protocol
- Restore isTopLevelWindow() guard for iframe security
- Revert syncUrlWithSessionKey signature (host param was unused)

* feat(ui): Token Usage dashboard with session analytics

Adds a comprehensive Token Usage view to the dashboard:

Backend:
- Extended session-cost-usage.ts with per-session daily breakdown
- Added date range filtering (startMs/endMs) to API endpoints
- New sessions.usage, sessions.usage.timeseries, sessions.usage.logs endpoints
- Cost breakdown by token type (input/output/cache read/write)

Frontend:
- Two-column layout: Daily chart + breakdown | Sessions list
- Interactive daily bar chart with click-to-filter and shift-click range select
- Session detail panel with usage timeline, conversation logs, context weight
- Filter chips for active day/session selections
- Toggle between tokens/cost view modes (default: cost)
- Responsive design for smaller screens

UX improvements:
- 21-day default date range
- Debounced date input (400ms)
- Session list shows filtered totals when days selected
- Context weight breakdown shows skills, tools, files contribution

* fix: usage dashboard data + cost handling (#8462) (thanks @mcinteerj)

* Usage: enrich metrics dashboard

* Usage: add latency + model trends

* Gateway: improve usage log parsing

* UI: add usage query helpers

* UI: client-side usage filter + debounce

* Build: harden write-cli-compat timing

* UI: add conversation log filters

* UI: fix usage dashboard lint + state

* Web UI: default usage dates to local day

* Protocol: sync session usage params (#8462) (thanks @mcinteerj, @TakHoffman)

---------

Co-authored-by: Jake McInteer <mcinteerj@gmail.com>

src/gateway/protocol/schema/sessions.ts

@@ -101,3 +101,19 @@ export const SessionsCompactParamsSchema = Type.Object(
   },
   { additionalProperties: false },
 );
+
+export const SessionsUsageParamsSchema = Type.Object(
+  {
+    /** Specific session key to analyze; if omitted returns all sessions. */
+    key: Type.Optional(NonEmptyString),
+    /** Start date for range filter (YYYY-MM-DD). */
+    startDate: Type.Optional(Type.String({ pattern: "^\\d{4}-\\d{2}-\\d{2}$" })),
+    /** End date for range filter (YYYY-MM-DD). */
+    endDate: Type.Optional(Type.String({ pattern: "^\\d{4}-\\d{2}-\\d{2}$" })),
+    /** Maximum sessions to return (default 50). */
+    limit: Type.Optional(Type.Integer({ minimum: 1 })),
+    /** Include context weight breakdown (systemPromptReport). */
+    includeContextWeight: Type.Optional(Type.Boolean()),
+  },
+  { additionalProperties: false },
+);