Add /delegate skill for multi-agent task delegation

[sebastientaggart]

Add a new /delegate skill that generates ready-to-paste prompts for delegating parts of a task to other AI agents (Gemini, Cursor, Codex, etc.) during the /start planning gate.

The skill is designed to run during Step 2 of /start — after investigation but before saying go. It uses context already loaded by /start (issue body, agent notes, branch info) to produce a scoped prompt with built-in rules: "do not commit" and "be surgical." Each delegation also tells the lead agent to skip that work when proceeding.

Changes:

• New skills/delegate.md source skill with generated output for all four adapters
• Updated /start Step 2 gates (both Case A and Case B) to mention /delegate as an option
• Added delegate to BRANCH_PROD and BRANCH_DEV used_in lists in config.schema.yaml

Issue #109

[sebastientaggart]

Review Summary

Verdict: APPROVE

Findings

No issues found.

The PR adds a new /delegate skill across all four adapters (Claude, Codex, Cursor, Gemini), updates /start to mention /delegate at both planning gates (Case A and Case B), and registers delegate in BRANCH_PROD and BRANCH_DEV used_in lists in config.schema.yaml.

All generated adapter files carry valid sync.py hashes. The source skill (skills/delegate.md) correctly uses {{BRANCH_DEV}} / {{BRANCH_PROD}} placeholders with established {{#if}} / {{#if !}} conventions. The skill is output-only (no commits, no GitHub writes), which keeps the blast radius minimal. The /start prompt changes are identical across all adapters and match the source.