docs: several commands missing from docs/commands.md reference

[agents-squads]

Problem

docs/commands.md is the command reference for humans and agents, but it omits a significant number of commands that are registered and working in the CLI.

Commands with no docs entry

Command	Purpose
squads log	Run history (timestamps, duration, status)
squads usage	Local token/cost view from executions.jsonl
squads runs	List live background agent runs (pid inventory)
squads kill [target]	Stop a background run gracefully
squads providers	Show available LLM CLI providers
squads commands	Dump the live command tree (machine-readable)
squads context / squads feed	Business context feed for agents
squads health	Quick infrastructure health check

Impact

• Agents invoking CLI commands for observability (squads log, squads usage) don't know these exist
• squads runs / squads kill are essential for background-run containment (cli#861 work) but have no docs
• squads providers is useful for multi-LLM routing decisions but undiscoverable
• squads commands is used by docs generation and skill drift detection — should be documented

Fix

Add these commands to the appropriate sections of docs/commands.md. Suggested placement:

• log, usage, runs, kill → "Monitor" section
• providers → "System" or "Setup" section
• context → "For Agents / Context" section
• commands → "System" section

Source: docs-eval agent