Remove Apex Dynamics faction, retune bullet speed/size

Drop Apex Dynamics from the playable roster (2 races now: Inner Sphere
Navy, Outer Rim Collective) to simplify the 2D art pipeline; World's
race-offer logic just shuffles both remaining races instead of picking
2 of N. Also fix bullets using a constant muzzle velocity instead of
adding the shooter's own velocity, and shrink the bullet hitbox/sprite.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

CLAUDE.md

@@ -40,6 +40,8 @@ README for how to run/extend it.
 
 18. **Engine-flame sprite swap on thrust** — 6 of item 17's 9 ships (ISN's Patriot/Barrage/Behemoth, ORC's Rail-Jack/Scrap-Spitter/Iron-Clad) gained a second `_flame.png` sprite alongside their idle one, cropped from the same concept sheets' flame-frame columns (ISN's sheet has a clean idle/flame pair per ship; ORC's only unambiguous case was Rail-Jack's brighter 3rd-column flame, so Scrap-Spitter/Iron-Clad's flame PNGs are just copies of their idle sprite for now — their sheet's other columns are damage/weapon-fire poses, not more exhaust). Behemoth's flame was composited from two separate sheet crops (clean idle hull + a flame-only crop of just its thrusters) rather than cropped directly, since the sheet's flame frame has a large red shield-ability graphic overlapping the hull that isn't exhaust. Apex's 3 ships (Lancet/Pulsar/Sovereign) have no flame art — their concept sheet never drew a thrust pose — so they're untouched and always show their one sprite. Wired into gameplay via a new optional `flame_path` per ship in `team_select.gd`'s `RACES`, threaded through `PlayerRegistry` (`submit_local_loadout`/`register_bot`/the loadout RPCs, new `ship_flame_path` field, default `""`) so bots and remote peers all get it too, not just the local owner. `ship_movement.gd`'s `_set_thrust_sprite()` swaps the `Sprite2D` texture based on whether the up/down thrust key is *currently held*, not current speed — this game's movement has no drag, so a first cut keyed off `velocity.length()` left the flame on long after letting off the gas since a released ship keeps drifting at speed. The owner predicts this locally the instant it samples input (`_owner_tick`); the server does the same for bots/itself (`_server_tick`) and broadcasts its authoritative value as a new `thrusting` bool on the existing `_receive_state` RPC so every other peer's view of a ship — which never sees raw input, only replicated state — stays in sync too, with no separate RPC needed. Ships with no `flame_path` (Apex) just skip the check entirely (`_flame_texture == null` short-circuits).
 
+19. **Apex Dynamics faction removed** — cut down to 2 playable races (Inner Sphere Navy, Outer Rim Collective) to simplify the 2D art pipeline. `team_select.gd`'s `RACES` array lost its Apex Dynamics block (Lancet/Pulsar/Sovereign), with ISN/ORC renumbered to `id` 1/2. `world.gd`'s `decide_offered_races()` no longer picks "2 of N" races — with only 2 total, that logic was vestigial, so it now just shuffles the order of both remaining races (kept for spawn-side/left-right variety, since `team_select.gd`/`ship_movement.gd` still key off `offered[0]`/`offered[1]`). `overview/racesclasses.md`'s faction-ability Rock-Paper-Scissors loop (which structurally needed 3 legs) is rewritten as a single ISN-shield-vs-ORC-mines counter relationship; `overview.md`/`bots.md`/`structure.md`'s "2 of 3 races" language updated to reflect both races always being fielded. `assets/images/ships/apex/` and `assets/sound/ships/apex/` are left on disk but unreferenced, same as the older unused `terran/mech/vorg` folders from item 17 — not deleted since that wasn't asked for.
+
 ## Current Tasks
 
 - [ ] Asteroids and environment hazards