Take planets by killing what defends them

#211 conquest is the fight now: a planet registers the garrison its setup
authors, each defender's own death counts against it, and the last one takes
the world. The capture points - stand in a ring, wait out a timer, once per
ring - are gone, along with the editor palette that placed them.
#212 conquest opens a dialog on the surface naming the research points
recovered; the award travels with the signal, after it is banked.
#209 the prologue's charted sectors go with the breach, so the map the
survivors keep is of where they now are - and "chart 30 sectors" is no
longer complete before they have flown anywhere.
#218 enemy variety is gated on the FLEET, not on wave strength: a starting
fleet meets chasers only at any wave number, and each vessel past three
opens one more kind.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_019AJMdB7iuHuLFZM1aBu3GD

tests/test_artillery_enemy.gd

@@ -17,7 +17,7 @@ extends SceneTree
 # Resolved via load() inside _initialize(), NOT a top-level `const ...
 # preload(...)` - a top-level preload in a script-mode ENTRY point (-s
 # this_file.gd) evaluates during this file's own early compilation, which
-# can happen before autoloads are registered. See test_capture_points.gd
+# can happen before autoloads are registered. See test_planet_garrison.gd
 # for the full explanation.
 var ARTILLERY_SHELL_SCRIPT: Script