feat(skills): default to creating new files, confirm before editing existing

[mandarnilange]

Summary

All three skills (`agentforge-workflow`, `agentforge-template-author`, `agentforge-debug`) bump to 0.2.0 with a unified Modification policy:

• Default behaviour: create new files alongside existing ones.
• Edits require explicit intent. Words like update, edit, modify, extend, rewrite, or naming the specific file. Without those, the skill creates a new file rather than touching the user's prior work.
• Per-file confirmation via `AskUserQuestion` (Claude Code) or the host agent's interactive-prompt tool. Skills propose the change in chat and wait for a yes/no — they never silently overwrite.

Per-skill specifics

• `agentforge-workflow` (the most invasive) — the policy applies to every file under `.agentforge/` (agents, pipelines, nodes, prompts, schemas). Greenfield runs are unaffected; the policy kicks in only when prior `.agentforge/` files exist.
• `agentforge-template-author` — applies to shipped templates, the registry, existing tests, and `docs/templates.md`. Editing a shipped template is flagged as a breaking change because end users `agentforge init --template ` against it. When the user's request overlaps with an existing template but they haven't asked to edit it, the skill now defaults to forking (`-secure`, `-v2`) instead of in-place modification.
• `agentforge-debug` — splits confirmation into two categories: state mutation (gate decisions, cancel / continue, claim clear) and file edits (prompts, schemas). Existing state-mutation rule preserved; new rule covers file edits in fix-path proposals. Substantive rewrites default to creating a new file alongside the existing one; one-line tweaks may edit in place after explicit confirmation.

Version bump rationale

Minor (0.1.0 → 0.2.0) per `skills/CHANGELOG.md` policy: additive behavioural guidance, new prose in `SKILL.md` and the Hard rules list. Trigger conditions unchanged — existing prompts still fire each skill.

Test plan

• `npm run skills:validate` — all three skills at 0.2.0, frontmatter valid.
• `npx biome check .` clean.
• CI `Publish Skills` workflow turns green.
• Manual validation: open a project with an existing `.agentforge/` directory, fire `agentforge-workflow` with a prompt that doesn't include "edit" / "update" — confirm the skill adds new files rather than overwriting.
• Manual validation: fire `agentforge-workflow` with "update the analyst agent to use claude-haiku-4-5" — confirm the skill asks per-file confirmation before editing `agents/analyst.agent.yaml`.