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>

CLAUDE.md

@@ -291,8 +291,8 @@ Agents specify their configuration in frontmatter using Claude Code's supported
 
 | Plugin | Agent | `model` | `permissionMode` | `disallowedTools` | `skills` |
 |--------|-------|---------|-------------------|--------------------|----------|
-| projman | planner | opus | default | — | body text (14) |
-| projman | orchestrator | sonnet | acceptEdits | — | body text (12) |
+| projman | planner | opus | default | — | frontmatter (2) + body text (12) |
+| projman | orchestrator | sonnet | acceptEdits | — | frontmatter (2) + body text (10) |
 | projman | executor | sonnet | bypassPermissions | — | frontmatter (7) |
 | projman | code-reviewer | opus | default | Write, Edit, MultiEdit | frontmatter (4) |
 | pr-review | coordinator | sonnet | plan | Write, Edit, MultiEdit | — |