Consolidate 30 skills → 1 zerion skill + fix init.js onboarding

[graysonhyc]

Summary

Fixes the onboarding pain evgen flagged in Slack: the picker showed 30 separate Zerion skills (mostly partner demos), install counts scattered, Claude Code wasn't auto-selected, and `npx -y zerion-cli init -y --browser` could stall when the CLI was already installed.

• Collapsed 30 `skills/zerion-` dirs into one `skills/zerion` skill with progressive disclosure. Capabilities (analyze, trading, sign, wallet, agent-management, swap-0x) live in `skills/zerion/capabilities/.md`. Partners (Bankr, Li.Fi, Moonpay, Vaults.fyi, Trails, Umbra, Somnia, Monad, Sendai, Uniswap, Consolidate) live in `skills/zerion/partners/*.md`. The root `SKILL.md` is ~150 lines and routes by task — capability/partner docs are loaded on demand via Read.
• `cli/commands/init.js`:
  • `ensureGlobalInstall` now short-circuits if `zerion --version` already resolves, even when invoked via npx temp dir (previously re-ran `npm install -g zerion-cli` on every npx call).
  • `installSkills` now auto-detects the host coding agent via env fingerprints (`CLAUDECODE`, `CURSOR_TRACE_ID`, `CODEX_HOME`, `GEMINI_API_KEY`) and fallback `~/.` dirs, then passes `-a ` to `npx skills add` so the 55-agent multi-select picker doesn't open.

What this fixes (from Slack)

1. 27+ skills polluting picker → now 1 entry (`zerion`).
2. Install counts scattered → single skill = single counter.
3. Bug: `init -y --browser` stuck when CLI installed → `which zerion` short-circuit + agent auto-pin removes the picker hang.
4. Claude Code not selected by default in picker → detected and passed via `-a claude-code` automatically.

Test plan

• `npm test` — 299/299 pass
• `node --check cli/commands/init.js`
• Manual: `npx -y zerion-cli init -y --browser` on a clean machine + a machine with global install
• Manual: verify Claude Code picker shows single `zerion` skill
• Manual: agent reads `capabilities/trading.md` correctly for a swap intent
• Manual: `gemini extensions install …` still works end-to-end
• Confirm install-count metric on agentskills.io now reports one slug

🤖 Generated with Claude Code