feat: CLI self-update command, update check, and wfctl mcp subcommand

[Copilot]

• Explore repository structure and understand existing code
• Add cmd/wfctl/update.go - self-update command + update check logic
• Add cmd/wfctl/mcp.go - mcp subcommand wrapping the MCP server
• Update cmd/wfctl/main.go - register update and mcp commands, version check on startup
• Add cmd/wfctl/update_test.go - tests for update check + self-update
• Add cmd/wfctl/mcp_test.go - tests for MCP command
• Update docs/mcp.md - document the new wfctl mcp command and migration notes
• Address review: set workflowmcp.Version = version in runMCP before creating server
• Address review: make checkForUpdateNotice truly non-blocking — returns done channel, command runs first, wait happens after command completes
• Address review: verify release asset integrity using checksums.txt from GitHub release
• Address review: replace downloadURL (no timeout) with downloadWithTimeout for binary downloads
• Address review: handle Windows — write .new.exe alongside current binary with instructions instead of failing os.Rename
• Address review: preserve existing binary file permissions instead of hardcoding 0755
• Address review: fix error format — single-line error, print hint to stderr separately
• Run linter - 0 issues
• Run tests - all pass

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[Copilot]

Pull request overview

Adds CLI self-updating and integrates the MCP server into wfctl to keep tooling aligned with engine/CLI releases, alongside documentation updates for MCP client configuration.

Changes:

• Introduces wfctl update (including --check) and a per-command update-availability notice.
• Adds wfctl mcp subcommand that runs the MCP server over stdio (delegating to the existing mcp package).
• Updates MCP documentation to prefer wfctl mcp and documents the update workflow.

Reviewed changes

Copilot reviewed 6 out of 6 changed files in this pull request and generated 7 comments.

Show a summary per file

File	Description
docs/mcp.md	Documents wfctl mcp as the preferred MCP entrypoint and adds update instructions.
cmd/wfctl/main.go	Registers new update/mcp commands and triggers update notices for most commands.
cmd/wfctl/update.go	Implements GitHub-release-based self-update, update checks, and update notices.
cmd/wfctl/update_test.go	Adds unit tests for release lookup, binary replacement, and update check flows.
cmd/wfctl/mcp.go	Implements wfctl mcp command wrapper around the mcp package server.
cmd/wfctl/mcp_test.go	Adds basic flag-parsing tests for the new mcp command.

[intel352]

@copilot apply changes based on the comments in this thread