fix(kyberforge): apply skill-audit findings to skill-author

Body discipline: collapsed 4-bullet script rules to single critical callout
(no interactive prompts); full contract stays in references/scripts.md.
stderr discipline: redirect all confirmation/progress output in new-skill.sh
to stderr per scripts.md contract. Also expands references/scripts.md with
input validation and --help guidance.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_016z2ZFYHQCex8yZAMVMTZzZ

plugins/kyberforge/skills/skill-author/references/scripts.md

@@ -70,10 +70,15 @@ Rules for all agentic scripts:
 - **Self-contained** — bundle dependencies inline so the agent can run the script with a single command; do not require a separate install step
 - **Structured output** — data (JSON, CSV) to stdout; diagnostics and progress to stderr
 - **Idempotent** — "create if not exists"; agents may retry on failure
+- **Input constraints** — validate inputs early; reject unknown or ambiguous values with a clear error rather than proceeding silently
 - **Meaningful exit codes** — `0` success, non-zero failure; document in `--help`
 - **Dry-run support** — add `--dry-run` for destructive operations; pair with `--confirm`/`--force` for operations that can't be undone
 - **Error messages** — on failure, state what went wrong, what was expected, and what to try; vague errors leave agents unable to self-correct
 
+## --help output
+
+Keep `--help` output concise — it enters the agent's context window. Include: usage line, one-line description, options with defaults, exit codes. Omit prose explanations.
+
 ## Output size
 
 Many harnesses truncate tool output beyond 10–30K characters. Default to a summary or a reasonable output limit. For scripts that can produce large output: support `--offset N` for pagination, or use `--output FILE` to write to disk and keep stdout clean.