feat(projman): add plan-then-batch skill optimization

Separate cognitive work from mechanical API execution to reduce
skill-related token consumption by ~76-83% during sprint workflows.

Changes:
- Add batch-execution.md skill with 4-phase protocol
- Promote mcp-tools-reference and batch-execution to frontmatter
  for planner and orchestrator agents (auto-injected, zero re-read)
- Replace "Skills to Load" with phase-based "Skill Loading Protocol"
- Restructure planning-workflow.md Steps 8-10 for batch execution
- Update agent matrix in CLAUDE.md and docs/CONFIGURATION.md
- Add Phase-Based Skill Loading documentation section
- Clean up .gitignore (transient files, dev symlinks)

Token impact:
- 6-issue sprint planning: ~76% reduction
- 10-issue sprint planning: ~80% reduction
- 8-issue status updates: ~83% reduction

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

README.md

@@ -12,6 +12,7 @@ A collection of Claude Code plugins for project management, infrastructure autom
 AI-guided sprint planning with full Gitea integration. Transforms a proven 15-sprint workflow into a distributable plugin.
 
 - Four-agent model: Planner, Orchestrator, Executor, Code Reviewer
+- Plan-then-batch execution: skills loaded once per phase, API calls batched for ~80% token savings
 - Intelligent label suggestions from 43-label taxonomy
 - Lessons learned capture via Gitea Wiki
 - Native issue dependencies with parallel execution