Ensure all tools have default initialize params

[mattlindsey]

Should help with patterns-ai-core/langchainrb_rails#111

[Copilot]

Pull Request Overview

This PR updates the initialization parameters for several tools to pull default values from environment variables, reducing the need for manual configuration.

• Update Weather, Tavily, GoogleSearch, and Database tools to use ENV variables as defaults.
• Modify the example usage and README to reflect the new default parameter behavior.

Reviewed Changes

Copilot reviewed 7 out of 7 changed files in this pull request and generated 1 comment.

Show a summary per file

File	Description
lib/langchain/tool/weather.rb	Sets default api_key from ENV["OPEN_WEATHER_API_KEY"].
lib/langchain/tool/vectorsearch.rb	Sets default vectorsearch from ENV["VECTORSEARCH_URL"].
lib/langchain/tool/tavily.rb	Sets default api_key from ENV["TAVILY_API_KEY"].
lib/langchain/tool/google_search.rb	Sets default api_key from ENV["SERPAPI_API_KEY"].
lib/langchain/tool/database.rb	Sets default connection_string from ENV["DATABASE_URL"].
examples/assistant_chat.rb	Removes redundant ENV param for Weather tool instantiation.
README.md	Updates TMDB tool initialization to use ENV["TMDB_API_KEY"].

[Copilot]

The default value from ENV['VECTORSEARCH_URL'] is a string while the documentation suggests a Langchain::Vectorsearch::Base instance is expected. Please ensure that this ENV variable is transformed into or replaced with an appropriate object.

Suggested change

	@vectorsearch = vectorsearch
	@vectorsearch = if vectorsearch.is_a?(String)
	Langchain::Vectorsearch::Chroma.new(url: vectorsearch, index_name: "default_index", llm: nil)
	else
	vectorsearch
	end