install_skill re-equip path never clears the disposed flag

[mega123-art]

Repro

1. Own a skill (bought via buy_skill).
2. unequip_skill(mint) — SKILL.md removed from claude/codex/openclaw/AGENTNET_SKILL_DIRS dirs, mint added to ~/.agentnet/skills.json's disposed array. Confirmed working.
3. install_skill(mint) (the documented re-equip path, plans/qa/external-hosts-qa.md §D.4) — SKILL.md correctly reinstalled to all dirs. Balance unchanged, as expected.
4. Check ~/.agentnet/skills.json — the mint is still in disposed.

Root cause

install_skill's tool handler (packages/core/src/skill-market/index.ts:343-370) calls SkillSync.installBoughtAll() / installBoughtToDir() directly. It never calls SkillSync.reEquip() (packages/core/src/skill-market/ingest/index.ts:249), which is the method that both restores the files AND calls undisposeNftSkill() to clear the flag.

Impact

Per the comment on disposed in registry.ts, the session-start owned-sync (injectOwned) skips any mint still in disposed. So a skill re-equipped via install_skill reinstalls now, but silently un-equips itself again on the next session start — even though the user just explicitly asked for it back, with no error or signal that this will happen.

Fix

Have the install_skill tool handler call SkillSync.reEquip() instead of (or in addition to, if a skill was never disposed) installBoughtAll/installBoughtToDir — or at minimum call undisposeNftSkill(skillId) alongside the existing install call.

Found during the QA run for issue #105 (Eliza + cross-host wrap-up), §D.3/D.4.