Register MCP servers through the installer

An MCP server is a URL plus a bearer token, and the token is why this is a
stage rather than a manifest line. Panama is public, so the tokens cannot
live in it, and neither runtime keeps its server list in a file worth
symlinking: Codex writes them into config.toml beside dozens of unrelated
settings, and Claude Code into ~/.claude.json. link-mcp registers them
through the runtime's own CLI instead.

user/agents/mcp/servers is tracked and names which variable carries each
token. user/agents/mcp/env holds the tokens and is ignored. A new machine
gets the servers by dropping its own env file beside the tracked one.

Only Claude Code is handled, and only where the interview enabled personal
content. Rewriting a section of somebody's live Codex TOML is a worse
failure mode than leaving two lines to paste once.

.gitignore

@@ -12,6 +12,10 @@
 /config/dot/espanso/match/identity.yml
 # Ignore backups of old config files
 /config/old
+# MCP bearer tokens. The server list in user/agents/mcp/servers is tracked
+# and names which variable carries each token; the tokens themselves are
+# machine-local, because this repo is public.
+/user/agents/mcp/env
 # Ignore Wireguard config of course!
 /config/wg/**
 # Ignore Neovim lazy-lock file