Orchestrator bypasses provider layer, breaking Copilot budget tracking

[maxbeizer]

Problem

The orchestrator calls o.agent.Execute() directly for plan/implement/review phases (orchestrator.go L442, L502, L616). This bypasses the provider layer entirely, which means:

• providers.Copilot.Execute() is never called
• IncrementRequestCount() never fires
• ~/.copilot/nightshift-usage.json is never written
• nightshift budget --provider copilot always shows 0% used

For Claude and Codex this is less impactful because they read usage from external files (~/.claude/stats-cache.json, ~/.codex/sessions/). But Copilot has no external usage file — the provider's request counter is the only tracking mechanism.

Reproduction

nightshift task run docs-backfill --provider copilot
# completes successfully, opens PR

nightshift budget --provider copilot
# shows 0% used — should show requests consumed

Suggested fix

Route agent execution through the provider layer so providers can hook into the execution lifecycle (tracking, rate limiting, cost estimation). Something like:

// Instead of:
execResult, err := o.agent.Execute(ctx, opts)

// Route through provider:
result, err := o.provider.Execute(ctx, task)
// provider.Execute() delegates to agent internally and handles tracking

This would also enable future features like per-provider rate limiting or cost-based model selection.

Context

Found while testing Copilot provider improvements (PRs #54, #55, #56). The provider Execute() method correctly increments the counter, but the orchestrator never calls it.

[marcus]

Hey @maxbeizer! Starling here (AI assistant on the project). 👋

This is a well-documented bug — the reproduction steps are clear and the proposed fix is sensible. The root cause (orchestrator calling agent.Execute() directly, bypassing provider.Execute()) is exactly the kind of shortcut that works fine until you need provider-level hooks.

Good context linking this back to PRs #54/#55/#56. I'm flagging this for Marcus — it's a small architectural decision (where the provider layer boundary sits) that he should weigh in on before we route the fix. Will get back to you. ✦