Add moon surface intro level with asteroid hazards and unarmed mechanics

Introduce moon01.lvl as the starting level — a pure jump-and-run intro
with no gun and no enemies, just platforming over gaps and dodging falling
asteroids. The player picks up their gun upon transitioning to level01.

New features:
- Moon tileset and PARALLAX_STYLE_MOON with crater terrain backgrounds
- Asteroid entity (ENT_ASTEROID): falls from sky, damages on contact,
  explodes on ground with particles, respawns after delay
- PLAYER_UNARMED directive disables gun for the level
- Pit rescue mechanic: falling costs 1 HP and auto-dashes upward
- Gun powerup entity type for future armed-pickup levels
- Segment-based procedural level generator with themed rooms
- Extended editor with entity palette and improved tile cycling
- Web shell improvements for Emscripten builds

src/game/player.h

@@ -33,6 +33,10 @@
 #define PLAYER_DASH_MAX_CHARGES  3  /* max jetpack charges           */
 #define PLAYER_DASH_RECHARGE  3.0f  /* seconds to recharge one charge*/
 
+/* Jetpack boost (from powerup) */
+#define PLAYER_JETPACK_BOOST_DURATION 15.0f /* seconds the boost lasts    */
+#define PLAYER_JETPACK_BOOST_RECHARGE  0.5f /* boosted recharge rate (s)  */
+
 /* Invincibility after taking damage */
 #define PLAYER_INV_TIME 1.5f       /* seconds of invincibility      */
 
@@ -56,6 +60,9 @@ typedef struct PlayerData {
     int     dash_max_charges;      /* max charges (for HUD)         */
     float   dash_recharge_timer;   /* time until next charge restored*/
     Vec2    dash_dir;              /* direction of current dash     */
+    float   jetpack_boost_timer;   /* remaining boost time (0=off)  */
+    /* Weapon */
+    bool    has_gun;               /* false until gun powerup picked up */
     /* Aiming */
     AimDir  aim_dir;               /* current aim direction         */
     bool    looking_up;            /* holding up without moving     */
@@ -84,7 +91,13 @@ float player_get_look_up_offset(const Entity *self);
 
 /* Get jetpack dash charge info for HUD (returns false if entity is not player) */
 bool player_get_dash_charges(const Entity *self, int *charges, int *max_charges,
-                             float *recharge_pct);
+                             float *recharge_pct, bool *boosted);
+
+/* Arm the player (give them the gun). Safe to call multiple times. */
+void player_give_gun(Entity *self);
+
+/* Check if the player has a gun */
+bool player_has_gun(const Entity *self);
 
 /* Check if the player is requesting a respawn (death anim finished + timer expired).
  * Returns true when respawn should occur. */