fix: hot reload plugin management changes (#75976)

Summary:
- The PR changes Gateway reload planning, CLI plugin install-index writes, plugin runtime/cache cleanup, docs, changelog, and tests so plugin enable/disable hot reloads while install/update/uninstall stay restart-backed.
- Reproducibility: yes. The earlier blocker has a source-level reproduction: run an external plugin install/up ...  watches config and only the managed plugin index changes; the PR now tests that path and queues a restart.

ClawSweeper fixups:
- Included follow-up commit: fix: hot reload plugin management changes
- Included follow-up commit: fix(clawsweeper): address review for automerge-openclaw-openclaw-7597…
- Ran the ClawSweeper repair loop before final review.

Validation:
- ClawSweeper review passed for head 860594f722.
- Required merge gates passed before the squash merge.

Prepared head SHA: 860594f722
Review: https://github.com/openclaw/openclaw/pull/75976#issuecomment-4363168379

Co-authored-by: Peter Steinberger <steipete@gmail.com>
Co-authored-by: clawsweeper <274271284+clawsweeper[bot]@users.noreply.github.com>

src/cli/plugins-update-command.ts

@@ -111,6 +111,9 @@ export async function runPluginUpdateCommand(params: {
         nextInstallRecords: nextPluginInstallRecords,
         nextConfig,
         baseHash: (await sourceSnapshotPromise)?.hash,
+        writeOptions: {
+          afterWrite: { mode: "restart", reason: "plugin source changed" },
+        },
       });
     } else {
       await replaceConfigFile({