Fix: deduplicate symlinked provider dirs during update and check

When .claude/skills is a symlink to .agents/skills, updating both
providers wrote to the same directory twice -- the last write
(.agents) always won, making .claude content identical to .agents.
The up-to-date check also always failed because it compared
provider-specific bundle content against the wrong provider's files.

Fix: use realpathSync to detect shared directories and process each
unique real path only once with its matching bundle provider. Respects
the user's symlink setup for non-impeccable skills.

Tested: first run updates 18 skills, second run reports "up to date".

CLI bumped to v2.1.6.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

package.json

@@ -1,6 +1,6 @@
 {
   "name": "impeccable",
-  "version": "2.1.5",
+  "version": "2.1.6",
   "author": "Paul Bakaus",
   "description": "Design skills, commands, and anti-pattern detection for AI coding agents",
   "keywords": [