Address TODO/FIXME markers in v5 codebase

[liliankasem]

Summary

There are 10 TODO comments across the v5 codebase indicating deferred work, incomplete implementations, or unresolved design questions. These should be triaged and addressed before GA.

TODO Inventory

Location	TODO
src/Func/Commands/Setup/SetupRunner.cs:933	Hardcoded stack package — should discover from workload metadata
src/Func/Commands/Start/Initialization/StartInitializationState.cs:41	Host env vars should move to proper host environment variable management
src/Func/Commands/Start/Initialization/Steps/InstallHostWorkloadInitializationStep.cs:90	Missing download progress reporting
src/Func/Bundles/InstalledBundleScanner.cs:44	Prerelease filter rule needs spec confirmation
src/Func/Commands/Workload/WorkloadSearchCommand.cs:93	--skip/--take paging UX not yet surfaced
src/Func/Workloads/Catalog/WorkloadPackageNotFoundException.cs:10	Needs UX-appropriate error messages
src/Func/Commands/Start/Azurite/Orchestration/ManagedAzuriteOrchestrator.cs:117	Mechanism needed to surface info beyond initialization
src/Workloads/ExtensionBundles/DownloadDefaultBundle.targets:24	Switch pack-time payload source from public CDN
src/Workloads/Workers/Node/Workloads.Workers.Node.csproj:17	Decouple from upstream worker's precise package layout
src/Workloads/Workers/Python/Workloads.Workers.Python.csproj:21	Decouple from upstream worker's precise package layout

Proposed Approach

Triage each TODO:

• Resolve now — if the fix is straightforward and blocks GA
• Convert to issue — if it represents significant work that can be tracked independently
• Remove — if the concern is no longer valid

Acceptance Criteria

• Each TODO is triaged (resolved, converted to issue, or removed with rationale)
• No remaining TODOs that represent GA-blocking incomplete functionality