feat: add token usage tracking, context display, and dynamic context length (#132)

* fix: specify TS_NODE_PROJECT for dev:server script

ts-node/register resolves tsconfig from the entry file upward,
finding the root solution-style tsconfig.json (no compilerOptions).
This causes target to default to ES3, breaking MapIterator spread
syntax (TS2802). Set TS_NODE_PROJECT env var to point to the server
tsconfig which targets ES2024.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

* feat: add token usage tracking, context display, and dynamic context length

- Intercept SSE proxy to capture run.completed events and persist token
  usage (input_tokens, output_tokens) per session to SQLite/JSON store
- Display context usage bar in ChatInput showing used/total/remaining tokens
- Resolve actual context length from Hermes models_dev_cache.json based
  on the active profile's default model (fallback 200K), with 5min in-memory cache
- Move sessions-db.ts to db/hermes/ for unified database layer
- Add usage store with SQLite + JSON fallback (auto-migration via ensureTable)
- Fix proxy SSE path regex to match rewritten upstream path
- Fix route ordering: /sessions/usage before /sessions/:id to avoid 404
- Fetch per-session usage on session enter instead of batch
- Add unit tests for usage-store, db index, and proxy SSE interception

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

---------

Co-authored-by: Claude Opus 4.6 <noreply@anthropic.com>

packages/client/src/api/hermes/chat.ts

@@ -28,6 +28,11 @@ export interface RunEvent {
   preview?: string
   timestamp?: number
   error?: string
+  usage?: {
+    input_tokens: number
+    output_tokens: number
+    total_tokens: number
+  }
 }
 
 export async function startRun(body: StartRunRequest): Promise<StartRunResponse> {

packages/client/src/api/hermes/sessions.ts

@@ -94,3 +94,26 @@ export async function renameSession(id: string, title: string): Promise<boolean>
     return false
   }
 }
+
+export async function fetchSessionUsage(ids: string[]): Promise<Record<string, { input_tokens: number; output_tokens: number }>> {
+  if (ids.length === 0) return {}
+  const params = new URLSearchParams()
+  params.set('ids', ids.join(','))
+  return request(`/api/hermes/sessions/usage?${params}`)
+}
+
+export async function fetchSessionUsageSingle(id: string): Promise<{ input_tokens: number; output_tokens: number } | null> {
+  try {
+    return await request<{ input_tokens: number; output_tokens: number }>(`/api/hermes/sessions/${id}/usage`)
+  } catch {
+    return null
+  }
+}
+
+export async function fetchContextLength(profile?: string): Promise<number> {
+  const params = new URLSearchParams()
+  if (profile) params.set('profile', profile)
+  const query = params.toString()
+  const res = await request<{ context_length: number }>(`/api/hermes/sessions/context-length${query ? `?${query}` : ''}`)
+  return res.context_length
+}