feat: straddle support in recorder

Add a straddle from any non-blind seat (default 2×BB) via a preflop control.
Recorded as a preflop post (fits the contract — order carries 'acts last'), tagged
straddle for the log label + removability; the UI-only flag is dropped from the
emitted structured hand. Blinds stay non-removable. Documented in HAND_HISTORY.md.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

docs/HAND_HISTORY.md

@@ -53,6 +53,9 @@ DB, no shared UI components. If RTO is down, Lyra skips analysis and nothing bre
 - **Positions:** `UTG UTG1 UTG2 MP LJ HJ CO BTN SB BB`.
 - **Actions:** `post fold check call bet raise allin`. `amount` is a plain number (no `$`),
   null for non-sized actions (fold/check). Street boards appear as `{street, board}` entries.
+  A **straddle** is recorded as a preflop `post` at a non-blind position (typically 2×BB,
+  voluntary); preflop action starts left of it and it acts last, but that's reflected by
+  action *order*, not a distinct verb.
 - **Streets:** `preflop flop turn river`.
 
 `lyra/poker.py:normalize_structured()` is the single function that guarantees this shape.