feat: sync shared vault at session start

plugins/shared-vault-sync/.claude-plugin/plugin.json

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+{
+  "name": "shared-vault-sync",
+  "version": "0.1.0",
+  "description": "Safely pulls the shared vault at interactive session start.",
+  "author": { "name": "Senkensha" },
+  "hooks": "./hooks/claude-codex-hooks.json"
+}

plugins/shared-vault-sync/.codex-plugin/plugin.json

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+{
+  "name": "shared-vault-sync",
+  "version": "0.1.0",
+  "description": "Safely pulls the shared vault at interactive session start.",
+  "author": {
+    "name": "Local developer"
+  },
+  "hooks": "./hooks/claude-codex-hooks.json",
+  "interface": {
+    "displayName": "Shared Vault Sync",
+    "shortDescription": "Safely pull the shared vault at session start.",
+    "longDescription": "Fast-forwards a clean shared vault at session start without blocking the agent when the network is unavailable.",
+    "developerName": "Local developer",
+    "category": "Productivity",
+    "capabilities": [
+      "Lifecycle hooks"
+    ],
+    "defaultPrompt": "Synchronize the shared vault."
+  }
+}

plugins/shared-vault-sync/README.md

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+# shared-vault-sync
+
+Pulls a clean shared vault at `SessionStart` without blocking Claude Code or Codex when the network is unavailable.
+
+Set `SHARED_VAULT_DIR` to the vault directory to sync it from any working directory. Without it, the hook acts only when the session starts inside a repository whose `AGENTS.md` identifies it as the shared persistent vault.
+
+The hook skips a dirty worktree and uses `git pull --ff-only`; it never rebases, merges, or pushes.
+
+## Install
+
+Install `shared-vault-sync` from the `infra-plugins` marketplace, then open a new session to activate its `SessionStart` hook.
+
+## Recommended push automation
+
+Keep pushes commit-driven. A scheduled local job may run `git fetch` and `git push` only when the vault is clean and the local branch is ahead; it must never rebase, force-push, or resolve conflicts. Let this hook handle the next safe pull after a rejected push.

plugins/shared-vault-sync/hooks/claude-codex-hooks.json

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+{
+  "hooks": {
+    "SessionStart": [
+      {
+        "hooks": [
+          {
+            "type": "command",
+            "command": "bash \"${CLAUDE_PLUGIN_ROOT}/hooks/pull-shared-vault.sh\"",
+            "timeout": 15,
+            "statusMessage": "Synchronizing shared vault..."
+          }
+        ]
+      }
+    ]
+  }
+}

plugins/shared-vault-sync/hooks/pull-shared-vault.sh

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+#!/usr/bin/env bash
+# Pull only the designated shared vault; never block a new agent session.
+set -u
+
+vault_dir="${SHARED_VAULT_DIR:-${PWD:-}}"
+
+emit() {
+  printf '{"continue":true,"suppressOutput":true,"hookSpecificOutput":{"additionalContext":"%s"}}\n' "$1"
+}
+
+if [ ! -f "$vault_dir/AGENTS.md" ] || ! grep -Fq 'This is the shared persistent vault' "$vault_dir/AGENTS.md" || ! git -C "$vault_dir" rev-parse --is-inside-work-tree >/dev/null 2>&1; then
+  emit 'Shared vault sync skipped: set SHARED_VAULT_DIR or start the session from the shared vault.'
+  exit 0
+fi
+
+if [ -n "$(git -C "$vault_dir" status --porcelain)" ]; then
+  emit 'Shared vault sync skipped: the worktree has local changes.'
+  exit 0
+fi
+
+if GIT_TERMINAL_PROMPT=0 git -C "$vault_dir" pull --ff-only --quiet; then
+  emit 'Shared vault sync completed.'
+else
+  emit 'Shared vault sync failed; run git pull --ff-only from the vault when it is safe to do so.'
+fi