fix(07-05): pay IN-01/IN-02/IN-03 — dead export gone, wrangler comment truthful, 900 s boundary pinned

- IN-01: delete the never-constructed ParsedInitData export (sole repo hit was
  its own declaration); the three read-helper catches now carry Intent:
  comments stating malformed-vs-tampered precedence and the chat-degrade law
- IN-02: wrangler.jsonc line 2 states the post-fact truth — the chat_sessions
  namespace id below is live, no re-creation
- IN-03: new T4 vector 'age 900 s → ok:true (the boundary is INCLUSIVE)' pins
  the strictly-greater comparator's inclusive edge (T-07-08); suite 126/126

bot/wrangler.jsonc

@@ -1,5 +1,5 @@
 {
-  // KV namespace id is filled in plan 03 task 1 after `npx wrangler kv namespace create chat_sessions`
+  // chat_sessions namespace created via `npx wrangler kv namespace create chat_sessions` — the id below is live.
   "name": "araharah-bot",
   "main": "src/webhook.ts",
   "compatibility_date": "2026-10-22",