feat: skills per-repo + additive multi-host deploy + remove iq host get (0.12.0)

[ccisnedev]

0.12.0 — finish the "everything repo-local, like git init" model (see #272/#274/#276), and revise the deploy model per evidence + user decision.

Decisions (approved)

• Per-repo + ADDITIVE: iq init --host X deploys agent + skills into the repo; does NOT delete other hosts (revises bug: switching host on an existing repo leaves the old agent and a stale config host #274's forced deletion). Rationale: OpenCode (.opencode/) and Claude (.claude/) have isolated discovery dirs — they coexist in one repo with no duplication, which is exactly what's needed to test qwen-vs-claude on the same repo. Only Copilot cross-reads (.github+.claude+.agents) → iq doctor warns on that combo instead of deleting.
• Remove iq host get; keep iq host clean (migration: remove stale global deploys).

Verified project skills paths

• Claude .claude/skills/<n>/SKILL.md · OpenCode .opencode/skills/<n>/SKILL.md (plural) · Copilot .github/skills/<n>/SKILL.md.

Scope

PR 1 (core):

• HostAdapter.projectSkillsRelPath; iq init --host X deploys skills per-repo (additive — drop _cleanOtherHostAgents).
• Move OpenCode/Ollama num_ctx auto-config (host/ollama: guarantee adequate context window for OpenCode (doctor must FAIL, host get must configure) #259/feat(host): iq host get --host opencode auto-configures Ollama num_ctx (#259 part 2) #262) from host get into iq init --host opencode.
• Remove iq host get; keep iq host clean. Migration: iq init removes the host's stale global skills.
• Embed inquiry-version marker in deployed agent + skills.

PR 2: iq doctor version-aware — scan deployed hosts in the repo, compare embedded version vs installed iq, warn on cross-read combos, don't fail on multi-host.

Codex host deferred. Goal: works on OpenCode/qwen; Claude validates.