fix: MCPServerCheck false negative in subdirectory projects

[anettodev]

Summary

mcs doctor permanently reported docs-mcp-server: not registered in subdirectory projects

ProjectDetector resolves the mcs project root to the subdirectory, but claude mcp add -s local keys entries in ~/.claude.json by the git root — causing MCPServerCheck to look at the wrong path.

Why is important?

Using mcs in a git subdirectory with CLAUDE.local.md is a supported use case, not an edge case.

mcs doctor is the primary health signal users rely on to know their configuration is correct — a permanent false negative on MCP server registration erodes trust in the tool and leaves users with no actionable fix path.

Changes

• MCPServerCheck.check() now walks up from the mcs project root to the git root when looking up projects[path].mcpServers in ~/.claude.json, matching how the Claude CLI determines the local scope key

Test plan

• swift test passes locally
• swiftformat --lint . and swiftlint pass without violations
• Affected commands verified with a real pack (e.g. mcs sync, mcs doctor)

Checklist for engine changes

• Any fix() implementation does cleanup/migration only — never installs or registers resources

[bguidolim]

Review Summary

The bug is valid — verified empirically and through Claude Code docs. Claude CLI keys local-scope MCP servers by the git root, while ProjectDetector.findProjectRoot() can return a subdirectory (when CLAUDE.local.md is found before .git/). This causes MCPServerCheck to look up the wrong path in ~/.claude.json.

What needs attention

1. Same bug exists in ConfigurationDiscovery.discoverMCPServers() (line 166)

mcs export from a subdirectory project will silently miss project-scoped MCP servers — same root cause, same direct projects[projectRoot.path] lookup:

// Export/ConfigurationDiscovery.swift:165-167
let projectEntry = projects[projectRoot.path] as? [String: Any]

Suggestion: Extract the walk-up logic into a shared utility (e.g., a static method on ProjectDetector like findGitRoot(from:), or a small helper that probes ~/.claude.json project keys walking up to .git/). Both MCPServerCheck and ConfigurationDiscovery should use it.

2. Missing tests

The walk-up loop has non-trivial termination logic (.git/ sentinel + / guard). CLAUDE.md requires integration tests for doctor check changes. Minimum needed:

• Subdirectory project root finds server keyed at git root → .pass
• Walk-up stops at .git/ boundary → doesn't escape the repo
• Regression: projectRoot == gitRoot still works

3. Minor simplification

candidate: URL? can be plain var candidate = root — deletingLastPathComponent() always returns a non-nil URL, so the optional wrapper is unnecessary.

What looks good

• Algorithm is correct: checks each ancestor before the .git/ break, so the git root itself is probed
• Well-bounded loop: terminates at both .git/ and /
• Edge cases handled: nil projectRoot, root == /, root == git root
• Minimal and focused change