Implement the following plan:

# Plan: Fix "something went wrong" / writing not saved bug

## Context
A Farcaster user reported: after writing, they saw "something went wrong" and their text wasn't saved.

Root cause: **`clearDraft()` is called at `home.html:1015` BEFORE the fetch fires**. If anything goes wrong — network error, Farcaster webview hiccup, slow connection — the draft is wiped from localStorage before the server even responds. The user's writing is permanently lost with no recovery path.

## Bug locations

**`templates/home.html` around line 1013–1051:**

```js
// Clear draft from localStorage — writing is being submitted
clearDraft();  // ← BUG: clears BEFORE server confirms success

fetch('/write', { method: 'POST', ... })
  .then(function(r) { return r.json(); })
  .then(function(data) { ... })
  .catch(function() {
    ankyBubble.innerHTML = '<span class="error">something went wrong.</span>';
    // text is gone, no retry possible
  });
```

Secondary bug: `.catch()` gives no recovery info and no retry path.

## Fix — `templates/home.html` only

**1. Remove `clearDraft()` from before the fetch.**

**2. Add `clearDraft()` inside the success `.then()`, only after `!data.error`.**

**3. In `.catch()`, since the draft was never cleared (fix 1), the draft is still in localStorage. Update the error message to tell the user their writing is preserved:**
```
"something went wrong — your writing is saved locally. reload to try again."
```

**4. Handle non-OK HTTP status** (e.g. 413 body too large) before calling `.json()` to avoid silent JSON parse failures.