Add scripted lightning weapon mods with interpolated anchored effects

mods/lightning_shield/README.md

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+# Lightning Shield
+
+An independent, reusable proximity weapon for **155,000 credits**. Enable
+**Lightning Shield** in the Mods menu, apply selections at the main menu, then
+buy it in the supply room. It is **always equipped** while owned and fires
+alongside the other primary guns when you hold **Fire**. It needs no special
+selection, consumes no ammo, and you can own one.
+
+Each pulse deals **2 damage** to up to **four close airborne ships** in any
+direction. Range is **28 logical pixels from your ship's center to the nearest
+point of the enemy hull**: approximately 12 pixels beyond your 32-pixel hull.
+It picks the nearest ships first, with a stable tie break. Ground structures
+are excluded. The **8-tick cooldown** gives about 2.92 pulses per second and
+5.87 measured damage per second against a stationary close ship.
+The price places this short-range supplement below the Micro Missile primary
+upgrade. See the [balance report](balance-report.json) for the 30-second
+controlled observations, including ground exclusions and combined loadouts.
+
+It runs only while Fire is held, and makes no sound when nothing is in range.
+It supplements close combat; it does not absorb collision damage, restore energy
+or block bullets. It continues working when you select a different special.
+
+Firing charges a flickering electric ring just outside the hull. The short zaps
+start from the edge facing each target, with a blue glow around the ship. The
+ring follows your movement and fades within one recharge after releasing Fire;
+it remains silent when no aircraft are close. The ring and its forks are cosmetic.
+
+This package uses the public mod API's `scripted` weapon behavior, read-only
+entity snapshots with `ground`, and `damage`, `arc` and `play_sound` commands.
+All targeting and damage rules live in `scripts/weapon.rhai`. It has no
+dependencies or overrides, and coexists with the other weapons and Iron Coast.
+
+The equipment icon ships in **16×16 SD** and **64×64 HD**, alongside the
+transparent source master and deterministic synthesized audio. The halo and
+connecting bolts use anchored `arc` commands and the game's renderer at both
+scales. See [provenance](ART_PROVENANCE.md)
+for the exact built-in imagegen prompt, asset hashes and reproduction recipes.
+
+From `RustRaptor/`:
+
+```sh
+cargo run --locked --no-default-features -- --mods mods --validate-mods lightning_shield
+cargo test --locked --no-default-features --test weapons_mods lightning_shield
+```
+
+See [weapon pricing and measurements](../../docs/weapon-balance.md),
+[the API](../../docs/modding-api.md) and
+[the AI mod checklist](../../docs/mod-authoring-checklist.md).