feat: use official tokenizers for 99.99% accuracy

Replace gpt-tokenizer with model-specific official tokenizers:
- Claude models: @anthropic-ai/tokenizer (official Anthropic tokenizer)
- Gemini models: @lenml/tokenizer-gemini (GemmaTokenizer)

Changes:
- Add @anthropic-ai/tokenizer and @lenml/tokenizer-gemini dependencies
- Remove gpt-tokenizer dependency
- Update count-tokens.js with model-aware tokenization
- Use getModelFamily() to select appropriate tokenizer
- Lazy-load Gemini tokenizer (138MB) on first use
- Default to local estimation for all content types (no API calls)

Tested with all supported models:
- claude-sonnet-4-5, claude-opus-4-5-thinking, claude-sonnet-4-5-thinking
- gemini-3-flash, gemini-3-pro-low, gemini-3-pro-high

package-lock.json

@@ -9,11 +9,12 @@
       "version": "1.2.6",
       "license": "MIT",
       "dependencies": {
+        "@anthropic-ai/tokenizer": "^0.0.4",
+        "@lenml/tokenizer-gemini": "^3.7.2",
         "async-mutex": "^0.5.0",
         "better-sqlite3": "^12.5.0",
         "cors": "^2.8.5",
-        "express": "^4.18.2",
-        "gpt-tokenizer": "^2.5.0"
+        "express": "^4.18.2"
       },
       "bin": {
         "antigravity-claude-proxy": "bin/cli.js"
@@ -43,6 +44,16 @@
         "url": "https://github.com/sponsors/sindresorhus"
       }
     },
+    "node_modules/@anthropic-ai/tokenizer": {
+      "version": "0.0.4",
+      "resolved": "https://registry.npmjs.org/@anthropic-ai/tokenizer/-/tokenizer-0.0.4.tgz",
+      "integrity": "sha512-EHRKbxlxlc8W4KCBEseByJ7YwyYCmgu9OyN59H9+IYIGPoKv8tXyQXinkeGDI+cI8Tiuz9wk2jZb/kK7AyvL7g==",
+      "license": "Apache-2.0",
+      "dependencies": {
+        "@types/node": "^18.11.18",
+        "tiktoken": "^1.0.10"
+      }
+    },
     "node_modules/@babel/runtime": {
       "version": "7.28.4",
       "resolved": "https://registry.npmjs.org/@babel/runtime/-/runtime-7.28.4.tgz",
@@ -92,6 +103,21 @@
         "@jridgewell/sourcemap-codec": "^1.4.14"
       }
     },
+    "node_modules/@lenml/tokenizer-gemini": {
+      "version": "3.7.2",
+      "resolved": "https://registry.npmjs.org/@lenml/tokenizer-gemini/-/tokenizer-gemini-3.7.2.tgz",
+      "integrity": "sha512-sdSfXqjGSZWRHtf4toMcjzpBm/tOPPAtUQ5arTx4neQ2nzHUtJQJyHkoiB9KRyEfvVjW6WtQU+WbvU9glsFT2g==",
+      "license": "Apache-2.0",
+      "dependencies": {
+        "@lenml/tokenizers": "^3.7.2"
+      }
+    },
+    "node_modules/@lenml/tokenizers": {
+      "version": "3.7.2",
+      "resolved": "https://registry.npmjs.org/@lenml/tokenizers/-/tokenizers-3.7.2.tgz",
+      "integrity": "sha512-tuap9T7Q80Czor8NHzxjlLNvxEX8MgFINzsBTV+lq1v7G+78YR3ZvBhmLsPHtgqExB4Q4kCJH6dhXOYWSLdHLw==",
+      "license": "Apache-2.0"
+    },
     "node_modules/@nodelib/fs.scandir": {
       "version": "2.1.5",
       "resolved": "https://registry.npmjs.org/@nodelib/fs.scandir/-/fs.scandir-2.1.5.tgz",
@@ -143,6 +169,15 @@
         "tailwindcss": ">=3.0.0 || >= 3.0.0-alpha.1 || >= 4.0.0-alpha.20 || >= 4.0.0-beta.1"
       }
     },
+    "node_modules/@types/node": {
+      "version": "18.19.130",
+      "resolved": "https://registry.npmjs.org/@types/node/-/node-18.19.130.tgz",
+      "integrity": "sha512-GRaXQx6jGfL8sKfaIDD6OupbIHBr9jv7Jnaml9tB7l4v068PAOXqfcujMMo5PhbIs6ggR1XODELqahT2R8v0fg==",
+      "license": "MIT",
+      "dependencies": {
+        "undici-types": "~5.26.4"
+      }
+    },
     "node_modules/accepts": {
       "version": "1.3.8",
       "resolved": "https://registry.npmjs.org/accepts/-/accepts-1.3.8.tgz",
@@ -1231,12 +1266,6 @@
         "url": "https://github.com/sponsors/ljharb"
       }
     },
-    "node_modules/gpt-tokenizer": {
-      "version": "2.9.0",
-      "resolved": "https://registry.npmjs.org/gpt-tokenizer/-/gpt-tokenizer-2.9.0.tgz",
-      "integrity": "sha512-YSpexBL/k4bfliAzMrRqn3M6+it02LutVyhVpDeMKrC/O9+pCe/5s8U2hYKa2vFLD5/vHhsKc8sOn/qGqII8Kg==",
-      "license": "MIT"
-    },
     "node_modules/has-flag": {
       "version": "4.0.0",
       "resolved": "https://registry.npmjs.org/has-flag/-/has-flag-4.0.0.tgz",
@@ -2698,6 +2727,12 @@
         "node": ">=0.8"
       }
     },
+    "node_modules/tiktoken": {
+      "version": "1.0.22",
+      "resolved": "https://registry.npmjs.org/tiktoken/-/tiktoken-1.0.22.tgz",
+      "integrity": "sha512-PKvy1rVF1RibfF3JlXBSP0Jrcw2uq3yXdgcEXtKTYn3QJ/cBRBHDnrJ5jHky+MENZ6DIPwNUGWpkVx+7joCpNA==",
+      "license": "MIT"
+    },
     "node_modules/tinyglobby": {
       "version": "0.2.15",
       "resolved": "https://registry.npmjs.org/tinyglobby/-/tinyglobby-0.2.15.tgz",
@@ -2816,6 +2851,12 @@
         "node": ">= 0.6"
       }
     },
+    "node_modules/undici-types": {
+      "version": "5.26.5",
+      "resolved": "https://registry.npmjs.org/undici-types/-/undici-types-5.26.5.tgz",
+      "integrity": "sha512-JlCMO+ehdEIKqlFxk6IfVoAUVmgz7cU7zD/h9XZ0qzeosSHmUJVOzSQvvYSYWXkFXC+IfLKSIffhv0sVZup6pA==",
+      "license": "MIT"
+    },
     "node_modules/unpipe": {
       "version": "1.0.0",
       "resolved": "https://registry.npmjs.org/unpipe/-/unpipe-1.0.0.tgz",