docs: hosted MCP is the only user path; fix own-entry echo in team updates

All users connect to https://useaxis.dev/api/mcp — remove the legacy npm
client option, the npx config blocks, and the CLI indexing examples from
README and mcp-setup (local server stays documented for contributors).

Also fix a live-observed bug in the team-update trailer: filtering per
LINE leaked indented continuation lines ("  Intent: ...") of an agent's
own multi-line notepad entries back to it. Authorship is now decided at
the entry head and applies to the whole entry.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>