Guardian boss bars; Phase 7 approved

Adrian, 2026-11-03: guardians get a boss health bar like the Wither's, which
also leads players to them. Every player within 128 blocks of a living
guardian sees a red bar of their own (GuardianBars): name, zone, how many
blocks away, and HP. The End boss keeps the dragon's bar.
guardian_appears_and_returns checks the bar appears and goes once beaten.
Self-tests and the island check pass.

Phase 7 approved ("Then begin with the next phase"); README status updated.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

docs/balance.md

@@ -42,6 +42,7 @@ Every tunable lives in a config file or in this table. **Placeholder** means gue
 | End spawns | the End is a zone, Lv 50–70; Cobblemon's End lines spawn there (Beheeyem, Reuniclus, Metagross; Gothitelle and Sigilyph in End cities; Malamar and Unown with a Poké Snack), all in the common bucket, each line's heaviest entry weight 10, Metagross 2 | Placeholder | `world/zones.json` → `dimensions` (`levels`, `bucket`, `line_weight`, `rare_factor`), then `tools/zone_layout.py` and `tools/zone_spawns.py` | Adrian, 2026-11-02: the End was barren; Lv 50–70 his pick |
 | Boss size | guardians about 8 blocks tall (Morpeko 4.9 at the 12× cap, Moltres 8, Regigigas 9.8 at the 1.5× floor); Eternatus 15 blocks; a cave guardian's spot needs that much air above it, else the roomiest floor within 24 blocks | Placeholder | `tools/zone_spawns.py` (`GUARDIAN_HEIGHT`, `GUARDIAN_SCALE_MIN`, `GUARDIAN_SCALE_MAX`), `tools/zone_bosses.py` (`END_HEIGHT`) | Adrian, 2026-11-02: way bigger. Area attacks that start at the boss reach half its width further |
 | Boss toughness | perfect IVs and 170 EVs each in HP, Defense and Sp. Def (510, the games' limit), nothing in Attack, Sp. Atk or Speed; in battle the Guardian's Ward: Defense and Sp. Def ×2 while defending, and one attack (all hits of a multi-hit move together) takes at most 25 % of max HP | Placeholder | `BossToughness.EVS`; `datapacks/core/data/cobblesurvival/held_items/guardiansward.js` (`DEF_FACTOR`, `SPD_FACTOR`, `HP_SHARE`) | Adrian, 2026-11-02: tougher, not stronger; the 25 % cap is his number. Applies to guardians, the End boss and practice copies |
+| Guardian boss bar | shown to each player within 128 blocks of a living guardian, updated every half second: name, zone, distance in blocks, HP | Placeholder | `GuardianBars.RANGE` | Adrian, 2026-11-03: like the Wither's, and it leads players to the guardian |
 | Machine look | a working core glows (light 10), its front animates (8 frames, 3 ticks each) and particles show; it keeps looking busy 2 s after the work stops; the Pokémon inside flinches (red flash, hit sound, no damage) about every 15 s while it works | Placeholder | `MachineBlock.ACTIVE_LIGHT`, `tools/machine_assets.py` (`FRAMES`, `FRAME_TICKS`), `MachineEffects` (particle and sound chances), `MachineBlockEntity` (`ACTIVE_LINGER`, `FLINCH_ONE_IN`) | Adrian, 2026-11-02. Working means: a heated furnace has something to cook, the generator isn't full, the synthesizer gets energy, a rebirth runs, the altar holds a Pokémon |
 | Level pressure | full experience up to 5 levels above the zone's band, then 10 % less per level, at least 10 % (Exp. Candy and commands exempt) | Decided (Adrian, 2026-10-30) | `world/zones.json` → `level_pressure` | E.g. on Button Isle (up to Lv 10): Lv 15 full, Lv 20 half, Lv 24+ a tenth |
 | Strong flyer | ridable through the air with top speed ≥ 60 or top stamina ≥ 85 (Cobblemon ride stats) | Decided (Adrian, 2026-10-30) | `tools/zone_spawns.py` (`STRONG_FLYER_*`) | 29 species |