Simple Taunt Announce - reborn

## 1.1.3 — Midnight secret boolean hotfix II (2025)

Follow-up hotfix to 1.1.2. Blizzard extended the secret boolean system to
`UnitIsUnit()`, which now returns a tainted proxy for non-player unit IDs
such as `"targettarget"`. This caused 1052 error spam per session.

### Bug fixes

- **`UnitIsUnit()` returns a secret boolean.** All five call sites replaced
  with a new `SafeUnitIsUnit(a, b)` helper that wraps the call in `pcall`
  and returns a plain Lua boolean. Affected paths:
  - Own-taunt detection (player / pet / vehicle check)
  - `findNewTank` loop (skip-self guard)
  - PATH B group-member guard

### Technical notes

Midnight's taint system now covers the return values of `UnitIsUnit`,
`UnitDetailedThreatSituation`, `UnitInRaid`, `UnitInParty`,
`GetRaidTargetIndex`, and `spellID` from `UNIT_SPELLCAST_SUCCEEDED`.
**Any boolean or identifier returned by a combat/unit API in Midnight
must be consumed through `pcall`.** Direct `if`/`not` tests will crash.

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