epic: Usage-based billing (Managed Agent Usage) RFC

[deansheather]

Usage-based Billing RFC

Phase 0:

• Implement license enforcement for AI agents #760
• Count managed agent usage and enforce limits in wsbuilder #777
• https://github.com/coder/nexus/issues/245
• Managed agent license usage frontend #813

Phase 1:

• Create usage-based billing package #814
• https://github.com/coder/tallyman/issues/1
  • https://github.com/coder/tallyman/issues/2

Note: between phase 1 and phase 2 will likely be a lot of non-product work required to get Metronome up and running before we give customers licenses.

Phase 2:

• https://github.com/coder/tallyman/issues/3
• Add usage section to deployment page in dashboard #817

Phase 3:

• https://github.com/coder/tallyman/issues/4

Phase 4:

• TBD