refactor(skills): remove zi-install, now in agent-skills (#741)

.github/instruction-surfaces.json

@@ -417,18 +417,6 @@
       "review_owner": "z-shell maintainers",
       "canonical_for": []
     },
-    {
-      "id": "skill-zi-install",
-      "path": ".github/skills/zi-install/SKILL.md",
-      "kind": "skill",
-      "authority": "advisory",
-      "consumers": ["agent", "human"],
-      "tasks": ["zi-installation", "zi-setup"],
-      "file_patterns": ["**"],
-      "required": false,
-      "review_owner": "z-shell maintainers",
-      "canonical_for": []
-    },
     {
       "id": "skill-create-readme",
       "path": ".github/skills/create-readme/SKILL.md",

knowledge/domains/zi/index.md

@@ -5,7 +5,7 @@ Select this domain for the plugin manager or Zi-specific annex behavior. Portabl
 | Task | Authoritative context |
 | --- | --- |
 | Understand the canonical manager decision | [ADR-0002](../../../decisions/0002-zi-as-canonical-plugin-manager.md) |
-| Install or update Zi | [Installation workflow](../../../.github/skills/zi-install/SKILL.md) and the [Zi repository](https://github.com/z-shell/zi) |
+| Install or update Zi | [`zi-install` skill](https://github.com/z-shell/agent-skills/blob/main/plugins/z-shell/skills/zi-install/SKILL.md) in `z-shell/agent-skills` and the [Zi repository](https://github.com/z-shell/zi) |
 | Understand promotion and release boundaries | [Branch model](../../../decisions/0019-trunk-on-main-default.md) and [promotion authorization](../../../decisions/0028-zi-promotion-is-release-authorization.md) |
 
 Read the owning Zi or annex checkout's instructions and current implementation before assuming an API, installation location or compatibility floor. End-user guides belong in the [wiki](https://wiki.zshell.dev/).

knowledge/domains/zi/repository-resources.md

@@ -6,7 +6,6 @@ Select a file for the task described below. Imported files have an editable know
 
 | File | Disposition | Purpose and reading context |
 | --- | --- | --- |
-| [.github/skills/zi-install/SKILL.md](../../../.github/skills/zi-install/SKILL.md) | referenced | Native skill package or supporting resource; read for its declared task. Keep capability mechanics with the skill and follow linked public procedures. |
 | [decisions/0002-zi-as-canonical-plugin-manager.md](../../../decisions/0002-zi-as-canonical-plugin-manager.md) | referenced | Historical decision record or generated decision index; inspect recorded status and supersession before applying it. Preserve numbering and accepted history. |
 | [decisions/0025-guided-setup-planner-first.md](../../../decisions/0025-guided-setup-planner-first.md) | referenced | Historical decision record or generated decision index; inspect recorded status and supersession before applying it. Preserve numbering and accepted history. |
 | [decisions/0028-zi-promotion-is-release-authorization.md](../../../decisions/0028-zi-promotion-is-release-authorization.md) | referenced | Historical decision record or generated decision index; inspect recorded status and supersession before applying it. Preserve numbering and accepted history. |

knowledge/repository-files.json

@@ -435,13 +435,6 @@
       "knowledge": "knowledge/domains/governance/repository-resources.md",
       "reason": "Native skill package or supporting resource; read for its declared task. Keep capability mechanics with the skill and follow linked public procedures."
     },
-    {
-      "path": ".github/skills/zi-install/SKILL.md",
-      "domain": "zi",
-      "disposition": "referenced",
-      "knowledge": "knowledge/domains/zi/repository-resources.md",
-      "reason": "Native skill package or supporting resource; read for its declared task. Keep capability mechanics with the skill and follow linked public procedures."
-    },
     {
       "path": ".github/skills/zsh-manual-research/SKILL.md",
       "domain": "zsh",