fix(install): strip ecc: plugin namespace from manual Claude installs

The ecc@ecc plugin namespaces agents, commands and skills as `ecc:<name>`.
A manual install (install-apply --target claude|claude-project) places the
same files at bare names under ~/.claude, so plugin-prefixed references in
copied markdown point at agents and commands that do not exist in that
layout (e.g. subagent_type "ecc:planner", frontmatter agent: ecc:...).

- Add plugin-namespace.js with stripPluginNamespace(), which removes the
  `ecc:` prefix before an identifier and leaves `ecc@ecc`, URLs and words
  ending in "ecc" alone.
- Apply it to markdown copy operations when the target is claude or
  claude-project. Non-markdown files and other targets are unchanged.
- Reword the agents rule so it describes both install modes instead of
  stating that agents only ship with the plugin.
- Cover the transform with tests/lib/install-plugin-namespace.test.js.

scripts/lib/install/apply.js

@@ -51,6 +51,11 @@ const {
   prepareExcludedPathsReconciliation,
 } = require('./excluded-paths-reconciliation');
 const { buildInstallIndex, rewriteRelativeLinks } = require('./link-rewrite');
+const { stripPluginNamespace } = require('./plugin-namespace');
+
+// Manual installs place agents, commands and skills at bare names; the
+// ecc@ecc plugin namespaces them as `ecc:<name>`.
+const MANUAL_CLAUDE_TARGETS = new Set(['claude', 'claude-project']);
 const { adaptAntigravityAgent } = require('./antigravity-agent');
 
 function isMarkdownPath(filePath) {
@@ -874,13 +879,16 @@ function applyInstallPlanLocked(plan, dependencies = {}, settingsLockHeld = fals
         && operation.sourceRelativePath
         && isMarkdownPath(operation.destinationPath)
       );
-      if (operation.kind === 'copy-file' && (operation.contentTransform || needsLinkRewrite)) {
+      const stripNamespace = MANUAL_CLAUDE_TARGETS.has(plan.adapter?.target)
+        && isMarkdownPath(operation.destinationPath);
+      if (operation.kind === 'copy-file' && (operation.contentTransform || needsLinkRewrite || stripNamespace)) {
         const transformed = transformInstallContent(
           operation,
           fs.readFileSync(operation.sourcePath, 'utf8')
         );
+        const namespaced = stripNamespace ? stripPluginNamespace(transformed) : transformed;
         const installedContent = needsLinkRewrite
-          ? rewriteRelativeLinks(transformed, {
+          ? rewriteRelativeLinks(namespaced, {
             sourceRel: operation.sourceRelativePath,
             index: linkIndex,
           })

scripts/lib/install/plugin-namespace.js

@@ -0,0 +1,19 @@
+'use strict';
+
+// The ecc@ecc plugin exposes agents, commands and skills under an `ecc:`
+// namespace (`ecc:planner`, `/ecc:plan`). A manual install
+// (install-apply --target claude|claude-project) places the same files at bare
+// names, so plugin-prefixed references in copied markdown must drop the prefix
+// or they point at agents and commands that do not exist in that layout.
+//
+// The leading guard keeps `ecc@ecc` and words that merely end in "ecc" (e.g.
+// "decc:") untouched; the lookahead requires a real identifier after the colon.
+const PLUGIN_NAMESPACE_PREFIX = /(^|[^A-Za-z0-9_@.-])ecc:(?=[a-z][a-z0-9-]*)/gm;
+
+function stripPluginNamespace(content) {
+  return String(content).replace(PLUGIN_NAMESPACE_PREFIX, '$1');
+}
+
+module.exports = {
+  stripPluginNamespace,
+};