Plugin system does not preserve execute permission on hook scripts

Description

When the plugin system syncs files from the cache directory to ~/.claude/plugins/marketplaces/, it does not preserve the execute bit (+x) on shell scripts. This causes hook scripts to fail with "Permission denied" errors.

Steps to Reproduce

1. Have the ralph-loop plugin installed (from the official marketplace)
2. Start a Claude Code session — the stop hook fails intermittently:

Stop hook error: Failed with non-blocking status code: /bin/sh:
/Users/<user>/.claude/plugins/marketplaces/claude-plugins-official/plugins/ralph-loop/hooks/stop-hook.sh: Permission denied

1. Running chmod +x on the script fixes it temporarily, but the next plugin sync resets permissions back to 644.

Root Cause

The cached copies of the script have mixed permissions:

# Cache (hashed versions) — correct:
-rwxr-xr-x  stop-hook.sh  (78497c524da3)
-rwxr-xr-x  stop-hook.sh  (61c0597779bd)

# Cache ("unknown" version) — missing +x:
-rw-r--r--  stop-hook.sh  (unknown)

# Marketplaces (active copy) — missing +x:
-rw-r--r--  stop-hook.sh

The plugin system copies files without preserving the execute bit, so the active copy under marketplaces/ ends up as 644 even though the source had 755.

Suggested Fix

Two complementary fixes:

1. Plugin system: Preserve file permissions when copying from cache to marketplaces/ (e.g., use cp -p or explicitly chmod +x *.sh after copy).
2. Hook execution: For hooks.json commands referencing .sh files, consider invoking them via bash <script> instead of relying on the execute bit, making execution independent of file permissions.

Workaround

Add to ~/.zshrc:

chmod +x ~/.claude/plugins/marketplaces/claude-plugins-official/plugins/ralph-loop/hooks/*.sh 2>/dev/null

Environment

• macOS (Darwin 25.2.0)
• Claude Code with official marketplace plugins