Expose durable workflow results to content-first MCP clients

[VikashLoomba]

Summary

• expose completed persisted workflow values through exact workflow://runs/{runId}/result resources with separately labelled script/result links
• add content-first compatibility for results up to 4,096 UTF-8 bytes and bounded action: "result" UTF-8 paging for larger values
• keep discovery, subscriptions, restart behavior, daemon notifications, and unavailable/corrupt/deleted states bounded and fail closed
• document the contract, regenerate selective authoring docs, and add an @automatalabs/mcp-server patch Changeset

Closes #423.

Testing

• pnpm build
• pnpm typecheck
• pnpm test
• pnpm --filter @automatalabs/codex-acp test
• node scripts/check-acp-deps.mjs
• pnpm changeset status --since=origin/main
• node scripts/check-attribution.mjs origin/main..HEAD
• AGENTPRISM_LIVE_E2E=1 npx tsx --test packages/mcp-server/test/live-backend.e2e.test.ts packages/acp-agents/test/steering.live.e2e.test.ts