Agent Skills: context-saver

Write the current session's in-flight work state to a human-readable handoff doc on disk (docs/context/CONTEXT-{topic}.md) so a future chat session — or another person — can pick up exactly where this one stops. Distinct from Claude Code's built-in memory system, which captures long-lived facts and preferences; this skill captures **active session context** (what's being built right now, which files are mid-edit, what's been tried, what's next). Use when the user says "save context", "checkpoint", "save progress", "preserve state", "save before I step away", "dump this so I can continue tomorrow", or before ending a long session with incomplete work. Optimizes for correctness, completeness, minimal size, and trajectory preservation.