Align mcp-server-dev skills with claude.com/docs connector guidance (#1418)

- build-mcp-server: load llms-full.txt for Claude-specific context;
  add Phase 6 (test in Claude, review checklist, submit, ship plugin)
- references/auth.md: add Claude auth-type table, callback URL,
  not-supported list
- references/tool-design.md: add Anthropic Directory hard requirements
  (annotations, name length, read/write split, prompt-injection rule)
- build-mcp-app: add Claude host specifics (prefersBorder,
  safeAreaInsets, CSP) and submission asset specs; testing via
  custom connector
- build-mcpb: note remote servers are the recommended directory path

plugins/mcp-server-dev/skills/build-mcp-server/references/auth.md

@@ -2,6 +2,22 @@
 
 Auth is the reason most people end up needing a **remote** server even when a local one would be simpler. OAuth redirects, token storage, and refresh all work cleanly when there's a real hosted endpoint to redirect back to.
 
+## Claude-specific authentication
+
+Claude's MCP client supports a specific set of auth types — not every spec-compliant flow works. Full reference: https://claude.com/docs/connectors/building/authentication
+
+| Type | Notes |
+|---|---|
+| `oauth_dcr` | Supported. For high-volume directory entries, prefer CIMD or Anthropic-held creds — DCR registers a new client on every fresh connection. |
+| `oauth_cimd` | Supported, recommended over DCR for directory entries. |
+| `oauth_anthropic_creds` | Partner provides `client_id`/`client_secret` to Anthropic; user-consent-gated. Contact `mcp-review@anthropic.com`. |
+| `custom_connection` | User supplies URL/creds at connect time (Snowflake-style). Contact `mcp-review@anthropic.com`. |
+| `none` | Authless. |
+
+**Not supported:** user-pasted bearer tokens (`static_bearer`); pure machine-to-machine `client_credentials` grant without user consent.
+
+**Callback URL** (single, all surfaces): `https://claude.ai/api/mcp/auth_callback`
+
 ---
 
 ## The three tiers