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/src/security/initdata.ts

@@ -56,15 +56,6 @@ export interface WebAppInitChat {
   photo_url?: string;
 }
 
-/** Shape of a fully parsed initData payload (hash/signature excluded from
- *  rawFields — they are auth metadata, not payload fields). */
-export interface ParsedInitData {
-  user: WebAppInitUser;
-  chat?: WebAppInitChat;
-  authDate: number;
-  rawFields: Map<string, string>;
-}
-
 export interface ValidateInitDataOptions {
   /** "Now" in seconds-since-epoch — injectable for deterministic tests. */
   nowSeconds?: number;
@@ -95,8 +86,9 @@ function parseFields(raw: string): Map<string, string> {
     try {
       fields.set(key, decodeURIComponent(value));
     } catch {
-      // Undecodable percent-escape — keep raw so HMAC compare fails ("tampered")
-      // rather than silently dropping the field.
+      // Intent: an undecodable percent-escape keeps the RAW value so the HMAC
+      // compare fails ("tampered") rather than silently dropping the field —
+      // malformed-vs-tampered precedence (D-14).
       fields.set(key, value);
     }
   }
@@ -160,6 +152,8 @@ export async function validateInitData(
         user = parsed as WebAppInitUser;
       }
     } catch {
+      // Intent: a malformed user payload is the "malformed" class, not a
+      // tampered one — the field never reaches the HMAC path.
       user = undefined;
     }
   }
@@ -209,6 +203,8 @@ export async function validateInitData(
         chat = parsedChat as WebAppInitChat;
       }
     } catch {
+      // Intent: a malformed chat payload degrades to "no chat context" (a
+      // private chat) — it never fails an otherwise-valid private-chat payload.
       chat = undefined;
     }
   }