test(mcp): add robust client-side behavioral tests for read-only and write modes

[SeeyaVhora]

What does this PR do?

This PR introduces comprehensive, client-side behavioral regression tests for the Model Context Protocol (MCP) server.

Following the fix in #3758 (which solved the read-only state desync issue), these tests ensure that the MCP server's read-only and write modes behave exactly as expected from the perspective of an actual MCP client.

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What is being tested?

Instead of just checking the internal state of the server, these tests use a real in-memory transport to interact with the server just like an MCP client would. We added four robust tests:

1. TestMCP_ToolsExposedViaProtocol:
   • Ensures that all 15 expected tools are successfully advertised over the MCP protocol in standard write mode.
2. TestMCP_AllToolsExposedInReadonlyMode:
   • Validates the important invariant that mutating tools (like deploy and delete) are still advertised when in read-only mode. (Read-only restrictions are enforced during execution, not by hiding the tools).
3. TestMCP_ReadonlyEnforcedAtRuntime:
   • Verifies that calling mutating tools (deploy and delete) in read-only mode returns a protocol-level error (IsError=true), as expected.
4. TestMCP_WriteModePermitsExecution:
   • Ensures that in standard write mode, the read-only guard is not triggered, permitting the client to execute these tools.

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Verification

All tests have been run and are passing:

go test -v ./pkg/mcp/...

• Result: PASS (including all new behavioral scenarios).

This builds directly on the work approved in #3758 to ensure we prevent future regressions.

[knative-prow]

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[knative-prow]

Hi @SeeyaVhora. Thanks for your PR.

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[SeeyaVhora]

Hi @lkingland,

As suggested in #3786, I've opened this follow-up PR to bring over the comprehensive client-side behavioral regression tests for the MCP server's read-only and write modes (since #3758 has merged).

To make the review process as clean as possible, I've structured the changes into 3 logical commits:

1. Tool advertisement/exposure protocol tests.
2. Runtime read-only enforcement checks.
3. Write-mode execution check with executor stubbing.

Whenever you have a moment, I'd appreciate it if you could take a look.