Add KingKong builtin template (Hard mode, ~2.5× Sun difficulty)

[ppXD]

Summary

Third builtin pet template, targeting the difficulty slot above Sun. Visuals: 10 sprites that arc from a black-stone egg through young silverback to a cyborg titan with a glowing gold gauntlet (final form).

Template	Difficulty	Display order	L99 cum
Unicorn	Easy	1	37,950
Sun (Wukong)	Medium	2	37,950
KingKong	Hard	3	47,436

Difficulty design — ~2.5× Sun

The rule_mult clamp floor of 0.5 means usage rules can't go any lower than Sun. So the 2.5× delta comes from two compounding levers:

Activity rules (chat is silent, milestones halved)

Rule	Sun	KingKong	Why
session_start	2	1	halved
user_prompt	1	0	chatting doesn't reward
assistant_stop	0	0	(unchanged)
tool_success	0	0	(unchanged)
task_completed	7	3	halved milestone
subagent_stop	5	2	halved milestone
pre_compact	1	0	eliminated

Net: only deliberate progress moves the meter (task done, subagent dispatched) plus AI token usage.

Level curve — 1.25× Sun

cum(L) = 200 + 188·(L-1) + 3·(L-1)²
  L1 = 200       (hatch — consistent across all builtins)
  L99 = 47,436   (Sun: 37,950 → ratio 1.250×)

Combined effect

Profile	Sun XP/conv	KingKong XP/conv	Total time vs Sun
Light (5t/conv)	12	~6	~2.5×
Medium (10t/conv)	29	~14	~2.6×
Heavy (15t/conv)	44	~21	~2.5×

Hits the design target across all usage profiles, not just one.

Display ordering — new display_order field

Adds meta.display_order: Option<i32> to TemplateMeta. EggPicker.tsx sorts by:

1. Source (builtin → community → custom)
2. display_order (lower first; absent → +Infinity, falls to tail)
3. Name alphabetically (tiebreaker)

So the picker now reads top-to-bottom: Unicorn → Sun → KingKong → [community/custom by name].

Visual + flavor

• Labels: "Hard" (black/gold) + "Challenge" (gold/black)
• Default pet name: KingKong
• Species flavor: "Forged in obsidian, ascending in titanium."
• Stage arc: obsidian egg → young primate → silverback → armoured stride → first circuits → cyborg legend

Coverage

• builtin_dirs_exist smoke test extended to assert kingkong/ is bundled via include_dir!
• New pick_template_kingkong_loads_and_creates_pet integration test pins end-to-end load + snapshot (matches the unicorn / sun canaries)
• 310/310 lib tests pass; desktop bundle + tsc --noEmit clean

Test plan

• Lib tests (310/310 stable)
• Desktop bundle cargo check clean
• tsc --noEmit clean
• After merge: launch app, EggPicker shows Unicorn → Sun → KingKong in that order
• Create a KingKong pet, verify no act-user-prompt events appear in xp_event (only task/subagent/session/usage)

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