v2.0.3 — Fix Pi extension loading

Fixes

• Pi extension loading: added "pi": { "extensions": ["./dist/index.js"] } to package.json — Pi requires this key to discover and load the extension; without it the package is installed but silently ignored
• Built JS: Pi loads compiled JavaScript, not TypeScript source. Added esbuild build step with prepublishOnly hook and CI build step
• Pi tool API: fixed handler → execute(_toolCallId, params) and added required label field
• Pi hook API: fixed event names (before_agent_start, session_compact) and system prompt injection (return { systemPrompt })
• Pi CLI installer: correctly uses pi install npm:@rohirik/pi-ltm (previous fix in 2.0.2)