feat: add agent loop health primitives

[andrei-hasna]

Summary

• add shared compact run summaries with output artifact refs and token/command counts
• add append-only run receipts linking run/task/conversation/knowledge/artifacts
• add loops health, loops audit, loops lint, loops runs --summary, and receipt CLI commands
• add MCP surfaces for run summaries, health, audit, lint, and receipt append/list
• document agent-oriented primitives and add CLI/MCP regression coverage

Adversarial review

• reviewer: Godel (019f0425-5333-7042-91ba-c2ee50836fba)
• reconciled blocking receipt leak by redacting persisted previews, target, issue, error, stdout, and stderr in receipt summaries
• added receipt cursor pagination, audit scan-limit metadata, never-run health semantics, and paged health summary generation

Validation

• bun run typecheck
• bun test src/cli/index.test.ts src/mcp/server.test.ts src/lib/store.test.ts
• bun test
• bun run build
• git diff --check
• local evidence: loops health, loops audit, loops lint, and receipt redaction smoke checks via bun run src/cli/index.ts

Task

• 26bb2e19-b478-4453-bce3-6187db3c1f5e