docs(mcp): correct trust fingerprint, store path, and auth UX

W1/W2: trust fingerprint covers sorted env key names (never values) with http-when-url-else-stdio type defaulting; store is ~/.corbits/trust/<repo-hash>.json keyed by first 32 hex of SHA-256 of the realpath-canonicalized root. W3: first-run auth is the mcp ! prompt-box mark plus Enter in /mcp opening the URL and auto-copying the link. W4/M1 intentionally skipped per spot-check: no root PLUGINS.md exists, and the briefed slug rule matches session/project-key.ts, not mcp/auth-store.ts.

Author: TheGreatAxios

docs/MCP.md

@@ -72,7 +72,11 @@ disabled or overridden by a custom `exa` MCP server. Other Exa MCP tools, such a
 **Project trust:** When `mcpServers` comes from **local** `.corbits/settings.json`,
 Corbits Code does **not** spawn or connect until each server is trusted for this
 project. Trust is stored as a fingerprint of `{ name, type, command, args, url }`
-in `~/.corbits/trust/<cwd-hash>.json` (outside the repo). The TUI prompts on
+plus the sorted `env` key names — never values, so adding a new injected
+variable invalidates a prior grant. `type` defaults to `http` when `url` is set,
+else `stdio`. The store lives in `~/.corbits/trust/<repo-hash>.json` (outside the
+repo), where `<repo-hash>` is the first 32 hex characters of the SHA-256 of the
+realpath-canonicalized project root. The TUI prompts on
 first connect (trust-on-first-use). Headless runs without a trust callback
 **fail closed** — untrusted local servers are not connected.
 
@@ -186,11 +190,11 @@ Because only `url` is set, `type` defaults to `http`.
 ### Authorization on first run
 
 The first time Corbits Code connects to an http server that requires auth, the TUI
-shows an authorization prompt listing the server and its authorize URL:
-
-- The URL is rendered as a clickable hyperlink (`open in browser`) in terminals
-  that support OSC 8.
-- Press **Alt+C** to copy the URL for pasting into a browser instead.
+marks the prompt box `mcp !` and lists the server as needing auth in `/mcp`.
+Focus the server in `/mcp` and press **Enter** to authorize: the authorize URL
+opens in the browser and the link is copied to the clipboard automatically (the
+copy covers SSH sessions, where the browser taking the redirect is often not
+this machine).
 
 Complete the consent flow in the browser. A loopback callback server catches the
 redirect and exchanges the authorization code for tokens automatically — the