fix(kyberforge): resolve agent-author audit findings

Corrects three FAIL findings from the skill-audit run:
- Scope detection table in SKILL.md and references/scripts.md now lists all
  four plugin-marker variants the script actually checks (plugin.json,
  .claude-plugin/plugin.json, .plugin/plugin.json, .github/plugin/plugin.json)
- assets/README.md copilot.agent.md description was wrong about field set;
  replaced with accurate CLI-format description noting excluded cloud/IDE fields
  and the Copilot tool aliases actually used.

Also applies the SUGGESTION: moves the conditional reference
(`If the destination is a plugin directory, read references/deployment-modes.md`)
out of the ## Gotchas section body and into ## Route as a standalone line,
immediately after ## Gotchas closes.

INFO findings (source_keys frontmatter) were already present in both
references/README.md and references/scripts.md — no change needed.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_0147vXtL5sP6vorDdqXGJJU9

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

@@ -24,7 +24,7 @@ Do not add additional substitution tokens unless you update both the template fi
 
 ## File placement
 
-The script creates files at paths determined by scope detection (plugin / project / user). Scope is detected from the presence of `plugin.json` or `.claude-plugin/plugin.json` in the root directory. If scope detection logic changes, update the `new-agent.sh` usage comment and `SKILL.md` Step 1 scope detection table in the same pass.
+The script creates files at paths determined by scope detection (plugin / project / user). Scope is detected from the presence of `plugin.json`, `.claude-plugin/plugin.json`, `.plugin/plugin.json`, or `.github/plugin/plugin.json` in the root directory. If scope detection logic changes, update the `new-agent.sh` usage comment and `SKILL.md` Step 1 scope detection table in the same pass.
 
 ## Error messages