feat(always-on): add maxPlansPerCycle config to cap plans per work cycle

[Gucc111]

Summary

• Add maxPlansPerCycle to AlwaysOnWorkspaceConfig (default: 3) to limit how many plans can execute in a single work cycle
• When the active cycle reaches the limit, new discovery fires are blocked until the user applies or archives the cycle
• The check runs in DiscoveryScheduler.tick() after standard gates pass, keeping evaluateAlwaysOnDiscoveryGates() as a pure function

Test plan

• Set alwaysOn.workspace.maxPlansPerCycle to 1 and verify that after one plan executes, subsequent ticks log cycle_full and do not fire
• Verify that after applying or archiving the cycle, the next tick proceeds normally and creates a new workspace
• Verify default value (3) works when no explicit config is provided
• Verify that invalid values (0, negative, non-integer) fall back to the default with a diagnostic warning

Made with Cursor