Add agent lifecycle XP integration test

[Vinaystwt]

Summary

Adds an end-to-end lifecycle test covering:

• agent registration
• task assignment
• task completion
• XP award
• level progression
• completed-task tracking

Also fixes a few gaps uncovered by the integration test:

• reject task assignment for unknown agents
• award XP when tasks are completed
• expose XP, level, and completed-task progress from the agent endpoint

Verification

• focused lifecycle tests passed
• nearby agent/task suites passed
• full test suite passed
• git diff --check passed

[sonarqubecloud]

Quality Gate passed

Issues
0 New issues
0 Accepted issues

Measures
0 Security Hotspots
0.0% Coverage on New Code
0.0% Duplication on New Code

See analysis details on SonarQube Cloud

[Vinaystwt]

Pushed the missing route changes that the lifecycle test depends on.

This wires the test through the actual API behavior:

• agent detail response now includes XP, level, and completed-task progress
• task completion awards XP
• task assignment rejects unknown agents with 404

The CI failure was because the test file was pushed without these route updates.