fix: set client_name in OAuth DCR and add --oauth-client-name flag

[jdormit]

Summary

• Sets client_name="mcp2cli" as the default in the OAuthClientMetadata used for OAuth Dynamic Client Registration (DCR)
• Adds --oauth-client-name flag to allow overriding the client name for servers that require a specific value

Problem

Some MCP servers require the client_name field in the RFC 7591 Dynamic Client Registration request body, but mcp2cli wasn't setting it:

• Honeycomb (mcp.honeycomb.io): returns 400 {"error":"invalid_client_metadata"} without client_name
• Figma (mcp.figma.com): restricts DCR to an allowlist of known client names — returns 403 Forbidden unless client_name matches an approved value (e.g. "Claude Code (figma)")

Fix

Commit 1: Always send client_name="mcp2cli" by default. This fixes servers like Honeycomb that just require the field to be present.

Commit 2: Add --oauth-client-name CLI flag (default: "mcp2cli") to allow overriding the value. This fixes servers like Figma that require a specific client name. The flag is also threaded through bake create/config so baked tools can persist a custom client name.

# Honeycomb works with the default
mcp2cli --mcp https://mcp.honeycomb.io/mcp --oauth --list

# Figma requires a specific client name
mcp2cli --mcp https://mcp.figma.com/mcp --oauth --oauth-client-name "Claude Code (figma)" --list

Verified that Notion (which already worked) continues to work with the default.

[knowsuchagency]

Thanks for the submission @jdormit !

[Christian-Sidak]

Opened a fix in #69 -- changes tool.get("inputSchema", {}) to tool.get("inputSchema") or {} so that an explicit null value (not just a missing key) is also treated as an empty schema, preventing the AttributeError crash. Two regression tests are included.