feature-create

Create a new feature in the project.

Before proceeding, check that CLAUDE.md contains a Feature Model section. If it doesn't, tell the user to run /feature-init first and stop.

The user has described the feature as: $ARGUMENTS

Steps:

1. Read FEATURES.md to understand existing features and avoid duplication.
2. Derive a short, descriptive slug for the feature (e.g. add-french-divisions, deploy-visualisation). Use lowercase-hyphenated format. Put that at the end of the feature title in square brackets as a tag (e.g. [add-french-divisions]).
3. Add a new entry at the top of the ## Pending section in FEATURES.md with the format:

### <Feature title> [tag]

<One or two sentences describing what the feature covers and why.>

Keep the description concise — no implementation detail, no sub-tasks. Those belong in a plan file created when the feature starts. If the user has provided requirements too detailed to fit in one or two sentences, preserve them in plans/<slug>.md under a ## Requirements section, noting that the Design section will be fleshed out when the feature starts. Do not create the plan file if there are no requirements beyond what fits in the FEATURES.md entry.

4. Confirm the new entry to the user as ready to proceed. Do not ask if they want to start the feature now (using /feature-start).