Add RSpec 'let' and 'let!' variable capture to scope parser

[Copilot]

RSpec let and let! variable declarations were not being captured by the scope parser, preventing code completion and navigation for these variables in test files.

Changes

• Added on_let_command handler in RspecCommands module to extract variable names from let(:name) syntax and register them in the current scope
• Added let! support via method_missing to handle the eager evaluation variant (method names with ! require special handling)
• Added test coverage for both let and let! variables in top-level and nested describe/context blocks

Example

describe UserController do
  let(:user) { User.create(name: 'Test') }        # Now captured as variable 'user'
  let!(:admin) { User.create(admin: true) }       # Now captured as variable 'admin'
  
  context 'when authenticated' do
    let(:token) { 'abc123' }                      # Captured in nested scope
    
    it 'returns users' do
      expect(user).to be_present                  # Variables available for completion
    end
  end
end

Variables are scoped within their containing describe/context blocks, matching RSpec's scoping semantics.

Original prompt

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This section details on the original issue you should resolve

<issue_title>rspec 'let' variables should show up</issue_title>
<issue_description>In rspec tests, 'let' variables should show up as variables for the appropriate scope</issue_description>

<agent_instructions>Make sure to add this to the RspecCommands</agent_instructions>

Comments on the Issue (you are @copilot in this section)

• Fixes rspec 'let' variables should show up #106

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[kwerle]

Just make this an alias of on_let_command.

[kwerle]

And this should no longer be needed?