chore: Bump version to 0.26.0

Release highlights:
- bd doctor --check-health for lightweight startup hook health checks
- --no-git-history flag to prevent spurious deletions
- gh2jsonl --id-mode hash for content-based ID generation
- Critical MCP protocol stdin fix (PR #400)
- Git worktree staleness fix (#399)
- Multi-part prefix support (#398)
- bd sync commit scope fix

Updated all component versions:
- bd CLI: 0.25.1 -> 0.26.0
- Plugin: 0.25.1 -> 0.26.0
- MCP server: 0.25.1 -> 0.26.0
- npm package: 0.25.1 -> 0.26.0

Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude <noreply@anthropic.com>

.claude-plugin/plugin.json

@@ -1,7 +1,7 @@
 {
   "name": "beads",
   "description": "AI-supervised issue tracker for coding workflows. Manage tasks, discover work, and maintain context with simple CLI commands.",
-  "version": "0.25.1",
+  "version": "0.26.0",
   "author": {
     "name": "Steve Yegge",
     "url": "https://github.com/steveyegge"