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>

tests/server/sessions-db.test.ts

@@ -63,7 +63,7 @@ describe('session DB summaries', () => {
       },
     ])
 
-    const mod = await import('../../packages/server/src/services/hermes/sessions-db')
+    const mod = await import('../../packages/server/src/db/hermes/sessions-db')
     const rows = await mod.listSessionSummaries(undefined, 50)
 
     expect(databaseSyncMock).toHaveBeenCalledWith('/tmp/hermes-profile/state.db', { open: true, readOnly: true })
@@ -124,7 +124,7 @@ describe('session DB summaries', () => {
       },
     ])
 
-    const mod = await import('../../packages/server/src/services/hermes/sessions-db')
+    const mod = await import('../../packages/server/src/db/hermes/sessions-db')
     const rows = await mod.listSessionSummaries('telegram', 2)
 
     expect(prepareMock).toHaveBeenCalledWith(expect.stringContaining('AND s.source = ?'))
@@ -218,7 +218,7 @@ describe('session DB summaries', () => {
       },
     ])
 
-    const mod = await import('../../packages/server/src/services/hermes/sessions-db')
+    const mod = await import('../../packages/server/src/db/hermes/sessions-db')
     const rows = await mod.searchSessionSummaries('docker', undefined, 10)
 
     expect(prepareMock).toHaveBeenCalledWith(expect.stringContaining('messages_fts MATCH'))
@@ -265,7 +265,7 @@ describe('session DB summaries', () => {
       },
     ])
 
-    const mod = await import('../../packages/server/src/services/hermes/sessions-db')
+    const mod = await import('../../packages/server/src/db/hermes/sessions-db')
     const rows = await mod.searchSessionSummaries('记忆断裂', undefined, 10)
 
     expect(likeAllMock).toHaveBeenCalledWith('记忆断裂', '%记忆断裂%')