flow-next-capture

# /flow-next:capture — agent-native conversation → spec A free-form discussion (or a `/flow-next:prospect` survivor) frequently produces enough material for a complete spec, but stops short of the formal `flowctl spec create` + `spec set-plan` heredoc documented in `CLAUDE.md`. Without an explicit synthesis step, that context decays — the next session loses the conversation, the spec never lands, and the user re-explains the same idea to `/flow-next:plan`. This skill IS the synthesis. The host agent (Claude Code / Codex / Droid) extracts the recent user turns, drafts a CLAUDE.md-shaped spec with **per-line source tags** (`[user]` / `[paraphrase]` / `[inferred]` / `[strategy:<track>]`), **writes the spec through existing flowctl plumbing, prints a compact summary, and offers to open it in the editor** (capture's saved-spec review in [docs/read-back.md](../../docs/read-back.md)). The capture request authorizes the write; there is no approve-and-write checkpoint. Substantive choices still use short questions. There is no Python synthesizer, no codex / copilot subprocess, no fast-model classifier. The host agent is already an LLM and does the work directly. flowctl provides thin spec plumbing (`spec create`, `spec set-plan`, optional `spec set-branch`, `memory search` for duplicate detection) plus the chart handoff callback (`chart link-spec`) after a successful chart-briefing capture. Capture never writes chart files and never mutates a chart's `ready` flag; chart never write...