MCP server configurations should inherit from parent directories

Problem

MCP server configurations in ~/.claude.json are keyed by exact project path and do not inherit from parent directories. This means launching Claude Code from a subdirectory will show "No MCP servers configured" even when a parent directory has MCP configs defined.

Current Behavior

Config in ~/.claude.json:

{
  "projects": {
    "/Users/username": {
      "mcpServers": {
        "datadog": { ... },
        "solarwinds-orion": { ... }
      }
    }
  }
}

Launch from subdirectory:

cd ~/git/tf-network/tf-network-idn
claude
# Result: "No MCP servers configured"

Claude Code looks for an exact match for /Users/username/git/tf-network/tf-network-idn, doesn't find it, and reports no MCP servers available.

Expected Behavior

Claude Code should walk up the directory tree to find MCP configurations:

1. Check /Users/username/git/tf-network/tf-network-idn → no config
2. Check /Users/username/git/tf-network → no config
3. Check /Users/username/git → no config
4. Check /Users/username → found!
5. Use parent's MCP configuration (with optional local overrides)

This is standard behavior in most development tools (git config, eslint, prettier, .editorconfig, etc.).

Why This Matters

1. User Experience: Users expect their MCP integrations (Datadog, Jira, etc.) to be available regardless of which subdirectory they're working in
2. Configuration Management: Forcing users to duplicate MCP configs for every subdirectory is error-prone and unmaintainable
3. Predictability: The current behavior is surprising - users don't understand why their MCP servers work from ~/ but not from ~/projects/foo

Suggested Solution

Implement hierarchical configuration lookup:

• Walk up directory tree to find first matching project config
• Allow subdirectories to define their own configs that override/extend parent configs
• Bonus: Support a true "global default" config that applies when no project-specific config exists

Workaround

Currently, users must either:

1. Always launch Claude Code from the root directory where MCP is configured
2. Duplicate MCP server configurations for every working directory (not recommended)