Remove 60 MB of the letter 'a' from spec/fixtures/vcr_cassettes (#287)

##

The majority of the installed size of the `ruby_llm` gem was simply
repeats of the letter `a`. This PR uses VCR's `filter_sensitive_data` to
avoid storing 60 million bytes of 'a' in `spec/fixtures/vcr_cassettes`.
:joy:

## Before

```
du -s spec/fixtures 
73448   spec/fixtures

ls -al chat_real_error_scenarios_*
10002062 chat_real_error_scenarios_anthropic_claude-3-5-haiku-20241022_handles_context_length_exceeded_errors.yml
10002198 chat_real_error_scenarios_bedrock_anthropic_claude-3-5-haiku-20241022-v1_0_handles_context_length_exceeded_errors.yml
10001980 chat_real_error_scenarios_deepseek_deepseek-chat_handles_context_length_exceeded_errors.yml
10001862 chat_real_error_scenarios_gemini_gemini-2_0-flash_handles_context_length_exceeded_errors.yml
10002399 chat_real_error_scenarios_openai_gpt-4_1-nano_handles_context_length_exceeded_errors.yml
10002014 chat_real_error_scenarios_openrouter_anthropic_claude-3_5-haiku_handles_context_length_exceeded_errors.yml
```

## After

```
du -s spec/fixtures 
14864   spec/fixtures

ls -al chat_real_error_scenarios_*
2202 chat_real_error_scenarios_anthropic_claude-3-5-haiku-20241022_handles_context_length_exceeded_errors.yml
2338 chat_real_error_scenarios_bedrock_anthropic_claude-3-5-haiku-20241022-v1_0_handles_context_length_exceeded_errors.yml
2120 chat_real_error_scenarios_deepseek_deepseek-chat_handles_context_length_exceeded_errors.yml
3207 chat_real_error_scenarios_gemini_gemini-2_0-flash_handles_context_length_exceeded_errors.yml
2539 chat_real_error_scenarios_openai_gpt-4_1-nano_handles_context_length_exceeded_errors.yml
2154 chat_real_error_scenarios_openrouter_anthropic_claude-3_5-haiku_handles_context_length_exceeded_errors.yml
```

Author: compumike

spec/fixtures/vcr_cassettes/chat_real_error_scenarios_anthropic_claude-3-5-haiku-20241022_handles_context_length_exceeded_errors.yml

@@ -73,7 +73,7 @@
           # Configure Psych to allow large input (JRuby's ext provider SnakeYAML has a low limit by default)
           Psych::Parser.code_point_limit = 20_000_000 if Psych::Parser.respond_to?(:code_point_limit=)
 
-          # Create a huge conversation
+          # Create a huge conversation (matching <MASSIVE_TEXT> in spec_helper)
           massive_text = 'a' * 1_000_000
 
           # Create a few copies in the conversation

spec/fixtures/vcr_cassettes/chat_real_error_scenarios_bedrock_anthropic_claude-3-5-haiku-20241022-v1_0_handles_context_length_exceeded_errors.yml

@@ -80,6 +80,9 @@
   config.filter_sensitive_data('<REQUEST_ID>') { |interaction| interaction.response.headers['Request-Id']&.first }
   config.filter_sensitive_data('<CF_RAY>') { |interaction| interaction.response.headers['Cf-Ray']&.first }
 
+  # Filter large strings used to test "context length exceeded" error handling
+  config.filter_sensitive_data('<MASSIVE_TEXT>') { 'a' * 1_000_000 }
+
   # Filter cookies
   config.before_record do |interaction|
     if interaction.response.headers['Set-Cookie']