Rename @mariozechner/pi-* to @earendil-works/pi-*

Pi moved to its new home at earendil-works on 2026-05-07
(https://pi.dev/news/2026/5/7/pi-has-a-new-home). Affected packages:

  @mariozechner/pi-coding-agent  -> @earendil-works/pi-coding-agent
  @mariozechner/pi-tui           -> @earendil-works/pi-tui
  @mariozechner/pi-ai            -> @earendil-works/pi-ai
  @mariozechner/pi-agent-core    -> @earendil-works/pi-agent-core

The old @mariozechner/* packages are deprecated on npm with the
explicit message 'please use @earendil-works/pi-coding-agent instead
going forward', and the version stream has moved on (old top-out
0.73.1; new currently 0.74.0). Anyone npm-installing the old names
gets a deprecation warning + a stale binary.

Sweep:
- All 7 extension TypeScript files: import statements updated.
- README, AGENTS, install.sh: textual references and the github.com/
  mariozechner/pi-coding-agent URL pointed at github.com/earendil-works/
  pi (the new monorepo root; coding-agent now lives at
  packages/coding-agent inside it).
- Bun build of mcp-loader, ext-toggle, ssh-controlmaster verified clean.

Brew install references (`brew install pi-coding-agent`) left as-is:
the homebrew formula still works at 0.73.1 and a tap update is
tracked upstream at earendil-works/pi#2755. Historical CHANGELOG
entries are untouched.

extensions/ext-toggle.ts

@@ -30,14 +30,14 @@ import * as os from "node:os";
 import {
   type ExtensionAPI,
   getSettingsListTheme,
-} from "@mariozechner/pi-coding-agent";
+} from "@earendil-works/pi-coding-agent";
 import {
   Container,
   Key,
   matchesKey,
   type SettingItem,
   SettingsList,
-} from "@mariozechner/pi-tui";
+} from "@earendil-works/pi-tui";
 
 const EXT_DIR = path.join(os.homedir(), ".pi", "agent", "extensions");