docs: add release-it bumper step to plugin checklist

.claude/skills/glean-plugin-checklist/SKILL.md

@@ -120,6 +120,27 @@ When releasing a new version:
 2. Update `package.json` version
 3. Update ALL `plugins/*/.claude-plugin/plugin.json` versions
 
+### 6. Add to .release-it.json bumper (REQUIRED)
+
+Path: `.release-it.json`
+
+Add an entry to the `plugins["@release-it/bumper"].out` array, after the last existing entry:
+
+```json
+{
+  "file": "plugins/<plugin-name>/.claude-plugin/plugin.json",
+  "path": "version"
+}
+```
+
+**If you skip this step**, the plugin version will fall behind the marketplace version on every future release. This failure is silent — no error will be thrown and no CI check will catch it.
+
+Verify the entry was added:
+
+```bash
+node .claude/skills/glean-plugin-checklist/scripts/check-bumper.mjs <plugin-name>
+```
+
 ## Verification Commands
 
 After adding a plugin, verify with:
@@ -138,6 +159,9 @@ done
 
 # Check README mentions the plugin
 grep "<plugin-name>" README.md
+
+# Check .release-it.json bumper includes the plugin
+node .claude/skills/glean-plugin-checklist/scripts/check-bumper.mjs <plugin-name>
 ```
 
 ## Common Mistakes to Avoid

.claude/skills/glean-plugin-checklist/scripts/check-bumper.mjs

@@ -0,0 +1,24 @@
+#!/usr/bin/env node
+// Check if a plugin is registered in the .release-it.json bumper.
+// Usage: node scripts/check-bumper.mjs <plugin-name>
+// Exit code 0 = found, 1 = missing
+
+import { readFileSync } from 'fs';
+
+const pluginName = process.argv[2];
+if (!pluginName) {
+  console.error('Usage: node scripts/check-bumper.mjs <plugin-name>');
+  process.exit(1);
+}
+
+const config = JSON.parse(readFileSync('.release-it.json', 'utf8'));
+const found = config.plugins['@release-it/bumper'].out.some(
+  o => o.file.includes(pluginName)
+);
+
+if (found) {
+  console.log('in bumper: ok');
+} else {
+  console.error(`MISSING from bumper: add plugins/${pluginName}/.claude-plugin/plugin.json to .release-it.json`);
+  process.exit(1);
+}

.gitignore

@@ -24,3 +24,6 @@ plugins/**/[0-9]*.[0-9]*.[0-9]*
 
 # Bun lockfile (not used in this project)
 bun.lock
+
+# Local planning documents
+docs/plans/