feat(templates): add budget tracking templates (Paperclip pattern)

Session 4 step 16 — post-hoc enforcement via PostToolUse hook with
PAUSED flag, budget-report.sh aggregates spend against window limit.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

scripts/templates/budget/BUDGET.md

@@ -0,0 +1,26 @@
+# Budget Policy: {{PROJECT_NAME}}
+
+## Company Budget
+- window: {{BUDGET_WINDOW}}
+- limit: {{BUDGET_LIMIT_CENTS}} cents
+- warn_percent: 80
+- hard_stop: true
+
+## Agent Budgets
+- {{AGENT_NAME}}: {{AGENT_BUDGET_CENTS}} cents/{{BUDGET_WINDOW}}
+
+## Notification
+- on_warn: log
+- on_hard_stop: pause
+
+## Notes
+
+Budget enforcement is POST-HOC (checked after each run, not before).
+This matches Paperclip's proven approach: check SUM(cost) after run,
+pause if exceeded. No pre-run reservation needed.
+
+Cost estimation uses token counts × published pricing. For accurate
+cost data, organizations can use the Admin API:
+`/v1/organizations/cost_report` (requires Admin API key: sk-ant-admin...).
+
+For headless runs, use `claude -p --max-budget-usd N` as a per-run cap.