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/server/src/controllers/hermes/sessions.ts

@@ -1,6 +1,8 @@
 import * as hermesCli from '../../services/hermes/hermes-cli'
 import { getConversationDetail, listConversationSummaries } from '../../services/hermes/conversations'
-import { listSessionSummaries, searchSessionSummaries } from '../../services/hermes/sessions-db'
+import { listSessionSummaries, searchSessionSummaries } from '../../db/hermes/sessions-db'
+import { deleteUsage, getUsage, getUsageBatch } from '../../db/hermes/usage-store'
+import { getModelContextLength } from '../../services/hermes/model-context'
 import { logger } from '../../services/logger'
 
 function parseHumanOnly(value: unknown): boolean {
@@ -84,9 +86,29 @@ export async function remove(ctx: any) {
     ctx.body = { error: 'Failed to delete session' }
     return
   }
+  deleteUsage(ctx.params.id)
   ctx.body = { ok: true }
 }
 
+export async function usageBatch(ctx: any) {
+  const ids = (ctx.query.ids as string)
+  if (!ids) {
+    ctx.body = {}
+    return
+  }
+  const idList = ids.split(',').filter(Boolean)
+  ctx.body = getUsageBatch(idList)
+}
+
+export async function usageSingle(ctx: any) {
+  const result = getUsage(ctx.params.id)
+  if (!result) {
+    ctx.body = { input_tokens: 0, output_tokens: 0 }
+    return
+  }
+  ctx.body = result
+}
+
 export async function rename(ctx: any) {
   const { title } = ctx.request.body as { title?: string }
   if (!title || typeof title !== 'string') {
@@ -102,3 +124,8 @@ export async function rename(ctx: any) {
   }
   ctx.body = { ok: true }
 }
+
+export async function contextLength(ctx: any) {
+  const profile = (ctx.query.profile as string) || undefined
+  ctx.body = { context_length: getModelContextLength(profile) }
+}