I think we may need to update the VCR cassettes here

I dug into the CI failures on this PR. There are two separate causes, and I've pushed a fixed version of this change to the claude/pr-328-test-failures-xihiq8 branch (this PR's commit plus a fix commit) with the full suite green locally (1287 runs, 0 failures, 0 errors) and bin/rubocop clean.

Why the 50 test failures happen

Every failing request body contains "tools":null — including plain requests with no MCP configuration at all:

POST https://api.anthropic.com/v1/messages with body
'{"model":"claude-sonnet-5","messages":[...],"max_tokens":1024,...,"tools":null}'

The chain is:

1. Anthropic::Request#apply_defaults sets mcp_servers: [] on every request (it's in DEFAULTS, see lib/active_agent/providers/anthropic/request.rb).
2. An empty array is truthy in Ruby, so the new if params[:mcps] || params[:mcp_servers] branch in normalize_params now runs unconditionally — even for requests that never touched MCP.
3. normalize_mcp_tools([]) returns nil (via .compact.presence), and params[:tools] = nil puts an explicit tools key into the gem model's data, which serializes as "tools": null in the request body.
4. Every WebMock body expectation in the integration suite then fails to match, since the expected bodies don't include a tools key. (Copilot's review also spotted this exact hazard.)

The fix is to only assign :tools when toolsets were actually extracted:

if params[:tools].nil?
  mcp_tools = normalize_mcp_tools(mcps)
  params[:tools] = mcp_tools if mcp_tools.present?
end

Why the lint job fails

The repo's RuboCop config (rails-omakase) enforces Layout/SpaceInsideArrayLiteralBrackets — array literals need spaces inside the brackets ([ "create_payment" ], not ["create_payment"]). The new tests in this PR have 28 such offenses. bin/rubocop -A on the touched files fixes them all.

Also included on the fix branch

While fixing the above I also addressed the Copilot review feedback:

• normalize_mcp_tools now accepts allowed_tools entries as tool-name strings/symbols as well as { name: ... } hashes (previously tool[:name] would raise TypeError on the string form shown in the MCP docs), ignoring entries in any other format, with test coverage for the string and mixed forms.
• normalize_mcp_tools now consistently returns nil whenever nothing is extracted (nil/non-array/empty input, or no allowed_tools), and the test names that said "returns empty array" but asserted nil were aligned with the actual behavior.

Feel free to cherry-pick 414821c from that branch onto this PR, or apply the equivalent changes directly.

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