feat: add expose API for clearweb publishing

[arthyn]

Adds API functions for the %expose agent which allows publishing Tlon posts to the clearweb.

New Functions

Core Operations

• listExposedContent() - Get all currently exposed posts
• checkPostExposed(citePath) - Check if a specific post is exposed
• exposePost(citePath) - Expose a post publicly
• hideExposedPost(citePath) - Hide an exposed post
• setExposeEagerMode(eager) - Toggle eager prefetching mode

Utilities

• expandCitePath(input) - Expand simplified paths to full cite format
• getExposedPostUrl(citePath, shipUrl) - Get the public URL for a post
• formatCite(cite) - Convert cite object to path string
• citePathToUrlPath(citePath) - Convert cite path to URL path

Usage

import { exposePost, listExposedContent, getExposedPostUrl } from '@tloncorp/api';

// Expose a post (simplified path format)
await exposePost('diary/~zod/blog/170.141.184.507...');

// List all exposed content
const exposed = await listExposedContent();

// Get public URL
const url = getExposedPostUrl('diary/~zod/blog/170.141...', 'https://zod.tlon.network');
// -> 'https://zod.tlon.network/expose/chan/diary/~zod/blog/note/170.141...'

Note

Requires the backend fix in tloncorp/tlon-apps#5507 to work correctly (fixes type mismatch in grab-post).