feat: add Pi origin support to code review UI (#263)

* feat: add Pi origin support to code review UI and update banner

Pi users were seeing "OpenCode" badge and getting the wrong update
command. Adds 'pi' to origin types in review/annotate servers, shows
violet "Pi" badge in code review header, and copies the correct
`pi install` command in the update banner.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

* feat: update Pi extension from install scripts when pi is available

The install scripts now check if `pi` is on PATH and run
`pi install npm:@plannotator/pi-extension` to update the extension.
Silent for users without Pi installed.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

---------

Co-authored-by: Claude Opus 4.6 <noreply@anthropic.com>

packages/server/review.ts

@@ -34,7 +34,7 @@ export interface ReviewServerOptions {
   /** HTML content to serve for the UI */
   htmlContent: string;
   /** Origin identifier for UI customization */
-  origin?: "opencode" | "claude-code";
+  origin?: "opencode" | "claude-code" | "pi";
   /** Current diff type being displayed */
   diffType?: DiffType;
   /** Git context with branch info and available diff options */