refactor: remove pricing field from TPMJS specification

Remove pricing field from the entire project as it doesn't make sense for tool metadata:

- Remove TpmjsPricingSchema and TpmjsPricing type from types package
- Remove pricing from TpmjsRichSchema validation
- Remove pricing from validateTpmjsField check
- Remove pricing documentation from /spec page
- Remove pricing examples from /publish page
- Remove pricing from HOW_TO_PUBLISH_A_TOOL.md
- Remove pricing from @tpmjs/createblogpost example package.json

The pricing field was removed from Tier 3 (Rich) metadata as it's not relevant for tool discovery and integration. Tools can document pricing in their README or documentation links instead.

🤖 Generated with [Claude Code](https://claude.com/claude-code)

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

packages/tools/createBlogPost/package.json

@@ -84,9 +84,6 @@
       "required": false,
       "type": "api-key"
     },
-    "pricing": {
-      "model": "free"
-    },
     "frameworks": ["vercel-ai", "langchain"],
     "links": {
       "documentation": "https://tpmjs.com/tools/createblogpost",