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/checklists/phase-7.md

@@ -11,6 +11,7 @@
 - **Arena:** leaving it (24 blocks; Basalt 32; End 40) or dying ends the battle as lost; the boss heals and stays. Automated: `boss_arena_leaving_loses`.
 - **The End:** the Ender Dragon is gone; Eternatus appears on the main island, with the dragon's boss bar; beating it opens the exit portal and gateway, leaves the egg the first time and gives experience. Automated: `end_boss_replaces_the_dragon`.
 - **Big and tough bosses** (Adrian, 2026-11-02): guardians stand about 8 blocks tall, Eternatus 15. Only HP, Defense and Sp. Def are raised (training, and the Guardian's Ward in battle doubles Defense and Sp. Def); no single attack takes more than a quarter of their HP. Guardians already in your world grow on the next check. Automated: `practice_bosses_spawn`, `boss_takes_a_quarter_per_attack`.
+- **Guardian boss bars** (Adrian, 2026-11-03): within 128 blocks of a guardian you see a red bar like the Wither's: its name, its zone, how many blocks away it is (which leads you to it) and its HP. Automated in `guardian_appears_and_returns`.
 - **End spawns:** the End is a zone (Lv 50–70) with Cobblemon's End lines: Beheeyem, Reuniclus, Metagross; Gothitelle and Sigilyph in End cities; Malamar and Unown with a Poké Snack. Automated: `end_has_spawns`.
 
 ## In game (Prism instance)
@@ -25,9 +26,12 @@ On the island save (or a new one), in creative or survival:
 - [ ] Find Regigigas in a Deep Dark cave and Moltres in the Basalt Furnace.
 - [ ] Go to the End: Eternatus is huge now (15 blocks). Fight it: no attack takes more than a quarter of its HP bar, even a super-effective one; it needs at least four hits. Its attacks are as strong as before.
 - [ ] Visit a guardian (`/cobblesurvival boss <zone>` spawns a practice copy next to you): about 8 blocks tall; Regigigas and Moltres stand in caves with room above them.
+- [ ] Walk towards a guardian's zone: within 128 blocks a red bar appears at the top ("Pinsir, guardian of Southwold (84 blocks away)"); the number drops as you get closer. In the fight the bar shows its HP; once it's beaten the bar goes.
 - [ ] Walk around the End's islands for a minute: Beheeyem, Reuniclus and now and then Metagross appear, Lv 50–70 (`/cobblesurvival zone` shows "The End").
 
 ## Ask Adrian
 
+**Phase 7 approved 2026-11-03** ("guardians should have a boss healthbar, like a wither … Then begin with the next phase"; the bar was built first).
+
 - Do the attacks feel dodgeable but dangerous? All numbers are placeholders (`docs/balance.md`).
 - Swap Moltres → Groudon, Eternatus → Giratina, Regigigas → Meloetta when Cobblemon adds their models? (one word each in `world/zones.json` / `tools/zone_bosses.py`)