Fix MCP experimental flag passed to wrong CLI command

[nikolay-1986]

Summary

Fixes the --experimental flag for the GitKraken MCP server not taking effect when enabled via gitlens.gitkraken.mcp.experimental.enabled setting.

Root cause

Commit e4abb9b ("Adds JSON-only setting for GK CLI --experimental flag") introduced the gitkraken.mcp.experimental.enabled setting and added code to pass --experimental to the CLI. However, the flag was appended to the gk mcp config command (the configuration query), not to the MCP server's runtime args.

The two-stage flow works like this:

1. Config query: GitLens runs gk mcp config vscode --source=gitlens --scheme=vscode to get the server definition
2. Server startup: VS Code starts the MCP server using the command and args from the config response

The mcp config subcommand does not recognize --experimental — it warns "unknown flag" and ignores it. Even if it did, the flag would only affect the config query, not the actual MCP server process. The returned args array never included --experimental, so the MCP server always started without experimental features.

Verified against CLI versions:

• gk.exe v3.1.55-rc.2 (bundled) — Warning: unknown flag: --experimental
• gk-insiders.exe v3.1.55-rc.3 — Warning: unknown flag: --experimental

Fix

• Moves --experimental injection from the config query args to the returned config.args array, so the MCP server itself receives the flag at startup
• Adds a guard (!config.args.includes('--experimental')) to avoid duplication if a future CLI version starts including it in the config response
• Registers gitlens.gitkraken.mcp.experimental.enabled in package.json so VS Code recognizes it as a valid setting (was only defined in src/config.ts TypeScript types)

Before (broken)

GitLens calls:  gk mcp config vscode --source=gitlens --scheme=vscode --experimental
CLI warns:      "unknown flag: --experimental"
CLI returns:    { args: ["mcp", "--host=vscode", "--source=gitlens", "--scheme=vscode"] }
Server starts:  gk.exe mcp --host=vscode --source=gitlens --scheme=vscode  ← no --experimental

After (fixed)

GitLens calls:  gk mcp config vscode --source=gitlens --scheme=vscode
CLI returns:    { args: ["mcp", "--host=vscode", "--source=gitlens", "--scheme=vscode"] }
GitLens adds:   args.push("--experimental")
Server starts:  gk.exe mcp --host=vscode --source=gitlens --scheme=vscode --experimental  ✓

Test plan

• Set "gitlens.gitkraken.mcp.experimental.enabled": true in settings.json
• Reload VS Code and verify the GitKraken MCP server starts with --experimental flag
• Verify experimental tools (e.g. git_status) appear in VS Code Copilot chat via @gitkraken
• Verify that with the setting set to false (default), --experimental is NOT appended
• Verify the setting appears as a recognized configuration in VS Code settings UI

🤖 Generated with Claude Code

[augmentcode]

🤖 Augment PR Summary

Summary: Fixes the GitKraken MCP experimental setting by ensuring the --experimental flag is applied to the MCP server startup args rather than the gk mcp config query.
Changes: Registers gitlens.gitkraken.mcp.experimental.enabled in package.json and appends --experimental to the returned config.args with a duplication guard.

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[ianhattendorf]

We're explicitly leaving this out of the package.json/contributions.json so it doesn't show in the settings UI.

[ianhattendorf]

This comment explains the fix, but doesn't really feel necessary or make sense out of context. It should probably just be removed.

[nikolay-1986]

I'm closing current PR, because the reason of the issue is on the CLI side when responding to the MCP config request https://github.com/gitkraken/gkcli/issues/722; the setting may also be hidden.