tests: Add Fleet and FleetAutoscaler tests

[NAME-ASHWANIYADAV]

Draft — depends on #25 and #26. Will be marked ready for review after those PRs merge and this branch is rebased.

Type of change

• 🐛 Bug fix
• 🚀 New feature / enhancement
• 📖 Documentation
• 🧹 Refactoring / cleanup
• ⚙️ CI / tooling
• ⚠️ Breaking change

What this PR does

Adds comprehensive unit tests for the Fleet and FleetAutoscaler resource models using the Vitest infrastructure introduced in #26.

Fleet tests (30 tests):

• scheduling, desiredReplicas, currentReplicas, allocatedReplicas, readyReplicas, reservedReplicas, strategy, maxSurge, maxUnavailable, allocationOverflow, priorities, counters, lists.

FleetAutoscaler tests (34 tests):

• fleetName, policyType, bufferSize, minReplicas, maxReplicas, currentReplicas, desiredReplicas, ableToScale, scalingLimited, lastScaleTime, lastAppliedPolicy, syncInterval.
• All policy types covered: Buffer, Webhook, Counter, List, Schedule (between + activePeriod), Wasm, Chain.

Did you use AI tools in preparing this PR?:
Y

Test plan

Automated checks

• npm ci
• npm run build
• npm run tsc
• npm run lint
• npm run format -- --check
• npm run test

All 121 tests pass across 5 test files (GameServer 29, Fleet 30, FleetAutoscaler 34, StateChip 13, buildAllocationBody 15).

Manual verification

N/A - unit tests only.

Notes for reviewers

All test data structures are verified against the upstream Agones Go structs (fleet.go, fleetautoscaler.go in agones-upstream/pkg/apis/agones/v1/).