Add the ability to disable caching when starting the server

[alzimmermsft]

What does this PR do?

Adds the option --disable-caching for starting the MCP server to disable caching of resources that can be cached, requiring repeated requests to fetch resources each time. And update starting the MCP server in testing to disable caching so all tests run all required requests to perform complete validation.

Also, slight change to where ICacheService is injected to always happen in ServiceStartCommand, removing it from being added in Program.cs (which should help improve CLI command performance as it is one less service that needs to be setup, and caching is pointless in CLI as everything it built and torn down for the one operation).

GitHub issue number?

[Link to the GitHub issue this PR addresses]

Pre-merge Checklist

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[Copilot]

Pull request overview

Adds a new server-start flag to disable resource caching and wires it through server host creation, with associated docs/test harness updates. It also relocates cache service registration for server hosts into ServiceStartCommand.

Changes:

• Add --disable-caching to server start options and bind it into ServiceStartOptions.
• Introduce NoopCacheService and conditionally register it (vs. existing cache services) when starting STDIO/HTTP hosts.
• Update Azure command docs and test harness defaults to start servers with caching disabled.

Reviewed changes

Copilot reviewed 14 out of 14 changed files in this pull request and generated 2 comments.

Show a summary per file

File	Description
servers/Template.Mcp.Server/src/Program.cs	Removes CLI-container cache registration (now expected to be handled during server start).
servers/Fabric.Mcp.Server/src/Program.cs	Removes CLI-container cache registration and updates warning comment.
servers/Fabric.Mcp.Server/changelog-entries/1775162068769.yaml	Adds changelog entry for --disable-caching.
servers/Azure.Mcp.Server/src/Program.cs	Removes CLI-container cache registration and updates warning comment.
servers/Azure.Mcp.Server/docs/azmcp-commands.md	Documents --disable-caching under azmcp server start.
servers/Azure.Mcp.Server/changelog-entries/1775162061580.yaml	Adds changelog entry for --disable-caching.
core/Microsoft.Mcp.Core/tests/Microsoft.Mcp.Tests/Client/LiveServerFixture.cs	Minor modernization of collection initialization.
core/Microsoft.Mcp.Core/tests/Microsoft.Mcp.Tests/Client/Helpers/McpTestUtilities.cs	Simplifies Process/ProcessStartInfo references.
core/Microsoft.Mcp.Core/tests/Microsoft.Mcp.Tests/Client/CommandTestsBase.cs	Starts test servers with --disable-caching.
core/Microsoft.Mcp.Core/src/Services/Caching/NoopCacheService.cs	Adds a no-op ICacheService implementation.
core/Microsoft.Mcp.Core/src/Services/Caching/CachingServiceCollectionExtensions.cs	Adds AddNoopCacheService DI registration helper.
core/Microsoft.Mcp.Core/src/Areas/Server/Options/ServiceStartOptions.cs	Adds DisableCaching option to server start options model.
core/Microsoft.Mcp.Core/src/Areas/Server/Options/ServiceOptionDefinitions.cs	Defines the new --disable-caching command-line option.
core/Microsoft.Mcp.Core/src/Areas/Server/Commands/ServiceStartCommand.cs	Registers/binds the new option and conditionally configures caching for STDIO/HTTP hosts.

[jongio]

Noop logic in extension methods (per vukelich's feedback) is a good approach. DI flow is correct - TryAdd in the CLI container lets the server host registration take precedence.

Issues to address:

• CachingServiceCollectionExtensions.cs:31 - disabled param needs a default value to avoid breaking existing callers
• ServiceStartOptions.cs:108 - cachingDisabled should be disableCaching to match other boolean options
• Azure.Mcp.Server/Program.cs:235 - comment dropped mention of ICacheService but it's still registered there

Note: 4 CI build configs are failing.

[jongio]

Looks good overall - DI wiring is correct and the feature works as intended. A few things to address:

Tests are incomplete:

• BindOptions_WithDefaults (ServiceStartCommandTests.cs:284) checks every other option's default but skips DisableCaching. Add Assert.False(options.DisableCaching).
• CreateParseResultWithAllOptions (ServiceStartCommandTests.cs:884) doesn't pass --disable-caching, and BindOptions_WithAllOptions doesn't assert it. Full round-trip binding isn't tested for this option.
• Consider adding DisableCachingOption_DefaultsToFalse to match the pattern every other boolean option follows.
• Only option parsing is tested - nothing validates that the DI container actually resolves NoopCacheService when the flag is set.

See inline comments for the other items (sealed, DI ordering comment, named arg).