chore: remove dead cli functions (batch 11)

[dsyme]

Removes 6 dead functions/types from pkg/cli/:

pkg/cli/docker_images.go

• ValidateMCPServerDockerAvailability — not used in production or tests
• PrintDockerPullStatus — not used in production or tests
• Removed unused fmt and os imports

pkg/cli/completions.go

• CompleteMCPServerNames — not used in production or tests

pkg/cli/preconditions.go

• PreconditionCheckResult type — only used by the deleted function
• CheckInteractivePreconditions — not used in production or tests
• checkGitRepositoryShared — only called by the deleted CheckInteractivePreconditions

Note: Other dead functions in pkg/cli/ (e.g., EnableWorkflows, ResetDockerPullState, etc.) were kept because they are used as test helpers or explicitly tested in unit tests.

[Copilot]

Pull request overview

Removes unused/dead CLI helpers from pkg/cli/ to reduce maintenance surface and eliminate now-unneeded imports.

Changes:

• Deleted interactive precondition helpers/types from pkg/cli/preconditions.go.
• Removed unused Docker availability/debug helpers and corresponding imports from pkg/cli/docker_images.go.
• Removed unused MCP server-name completion helper from pkg/cli/completions.go.

Reviewed changes

Copilot reviewed 3 out of 3 changed files in this pull request and generated no comments.

File	Description
pkg/cli/preconditions.go	Removes dead interactive precondition wrapper/type and an unreferenced git-repo helper.
pkg/cli/docker_images.go	Removes unused exported Docker availability check and debug printer; drops unused fmt/os imports.
pkg/cli/completions.go	Removes an unused MCP server completion helper.

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