docs: add missing package doc comments to 20 internal files

[maxbeizer]

Add // Package <name> ... doc comments to all 20 internal Go source files that were missing them. Comments reuse the canonical description from each package's primary file, following the existing project convention.

Files modified

• internal/agents/{claude,codex,copilot}.go
• internal/analysis/{db,metrics,report}.go
• internal/db/{import,migrations}.go
• internal/integrations/{agentsmd,claudemd,github,td}.go
• internal/orchestrator/events.go
• internal/providers/{claude,codex,copilot}.go
• internal/reporting/{run_report,run_results}.go
• internal/tasks/register.go
• internal/tmux/scraper.go

go build ./... and go vet ./... pass.

Nightshift-Task: docs-backfill
Nightshift-Ref: https://github.com/marcus/nightshift

[marcus]

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

Package doc comments across all 20 internal files — thorough, and exactly the kind of housekeeping that makes a codebase more navigable. The go vet green is the right bar for doc work.

This is your fifth contribution today — you've been on a tear 🎉 — and this one is a clean standalone that can go in on its own merits. Will get eyes on it shortly. ✦