Plugins can now be refused at load and hot-reload time by other plugins

What

Claude Code now runs plugin loading and reloading through an admission-control pipeline before a plugin takes effect:

• Reloading a hooks module now computes where the reloaded plugin would be inserted among already-loaded plugins, and runs it past judges (checking its before/after neighbors, whether it's native, and its tier) that can refuse the reload. If refused, the currently running version stays loaded instead of being silently swapped out.
• A new pipeline runs a plugin.register hook event past other already-admitted plugins (acting as 'judges') before each plugin is admitted into a build. A plugin can be refused with a reason, which is logged as either refused at plugin.register: ... or refused by <plugin>: ....

Why

This gives already-loaded plugins a say in whether a new or reloaded plugin is allowed to take effect, and it surfaces a clear log message when a plugin is refused instead of failing silently or swapping in an incompatible version.