feat(kyberforge): add agent-author skill for Claude Code and Copilot CLI agents

## Why

skill-author explicitly excludes agent definition files ("Do not use to author
agent definition files"). No factory skill existed to create or improve the
.md / .agent.md files that define Claude Code subagents and Copilot CLI agents
in a plugin, project, or user scope. This fills that gap.

## Implementation Notes

Single-root scaffold convention: new-agent.sh <name> <root> derives both
provider file paths from the root by convention — plugin scope (plugin.json
present) writes both files into <root>/agents/; non-plugin scope writes
.claude/agents/<name>.md and .github/agents/<name>.agent.md. This keeps
input minimal while always generating both provider files. See ADR-0015.

Routing is file-level (not directory-level like skill-author): neither file
exists → create flow; at least one exists → improve flow; scaffold is a
file-by-file no-op so retries are safe.

No companion agent-audit skill — inline validation in the close step covers
the simpler agent field contract. agent-audit is tracked as a follow-on.

## Impact

Closes the skill-author gap for agent definitions. Follow-ons tracked in
Gitea #11: agent-audit skill and --copilot-dest override flag for non-standard
Copilot project paths.

---
ADR: docs/adr/0015-agent-author-dual-provider-scaffold.md
Refs: #10
Co-authored-by: Claude Sonnet 4.6 <noreply@anthropic.com>

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

@@ -0,0 +1,9 @@
+# references/
+
+## deployment-modes.md
+
+Agent scope hierarchy, precedence rules, and per-scope restrictions. Covers: which fields are silently ignored for plugin agents (Claude Code and Copilot CLI), scoped identifiers for plugin subdirectory agents, cache isolation behaviour, and Copilot CLI path conventions. Loaded conditionally from SKILL.md when the destination is a plugin directory.
+
+## sources.md
+
+Research provenance record for this skill. Lists the upstream research sources (claude-code-plugins and github-copilot-plugins research docs) that informed SKILL.md, the templates, and the deployment-modes reference. Used by `skill-audit` to validate the provenance chain.

plugins/kyberforge/skills/agent-author/references/deployment-modes.md

@@ -0,0 +1,63 @@
+---
+source_keys:
+  - context7-websites-code-claude
+  - claude-code-plugins-docs
+  - claude-code-subagents-docs
+  - github-custom-agents-configuration
+  - github-cli-plugin-reference
+---
+
+# Agent Deployment Modes
+
+Agent definitions deploy at three scopes and behave differently at each. The scope determines which fields are honoured, where files must live, and what identifiers users invoke.
+
+## Scope hierarchy and precedence
+
+| Scope | Claude Code path | Copilot CLI path | Who it affects |
+|---|---|---|---|
+| User | `~/.claude/agents/` | `~/.copilot/agents/` | All sessions for this user |
+| Project | `.claude/agents/` | `.github/agents/` or `.copilot/agents/` | This repo only |
+| Plugin | `<plugin>/agents/` | `<plugin>/agents/` | Sessions with the plugin installed |
+
+When the same agent `name` appears at multiple scopes, **user scope wins over project scope wins over plugin scope** in Claude Code. In Copilot CLI, repo-level agents override enterprise and org-level; home-directory (user) agents override repo-level on name collision.
+
+## Plugin scope restrictions
+
+Plugin agents (agents shipped inside a plugin's `agents/` directory) have fewer capabilities than project or user agents:
+
+**Claude Code — silently ignored for plugin agents:**
+- `hooks` — per-agent event handlers; copy the agent to `.claude/agents/` to use these
+- `mcpServers` — inline MCP server definitions; not available in plugin context
+- `permissionMode` — silently ignored; the parent session's permission mode applies
+
+**Copilot CLI — unsupported or ignored:**
+- `mcp-servers` — cloud agents only; ignored in VS Code and most IDEs
+- `metadata` — key-value annotations; ignored in VS Code
+
+## Scoped identifiers (Claude Code plugin agents only)
+
+Plugin agents in **subdirectories** get compound identifiers:
+
+```
+plugins/my-plugin/agents/review/security.md  →  my-plugin:review:security
+```
+
+Users must invoke with `@agent-my-plugin:review:security`. **Keep agents flat in `agents/` to avoid this** — subdirectory nesting is rarely worth the UX cost.
+
+At project and user scope, subdirectory path does not affect the agent's name.
+
+## Cache isolation
+
+When a plugin is installed, its directory is copied to a cache. **Any path that leaves the agent's plugin directory breaks post-install.** Agent definition files must be self-contained — they cannot reference scripts, templates, or shared files outside the plugin.
+
+Agents at project or user scope are read directly from disk; cache isolation does not apply.
+
+## Copilot CLI path conventions
+
+| Scope | Expected path | Notes |
+|---|---|---|
+| User | `~/.copilot/agents/<name>.agent.md` | Home directory |
+| Project | `.github/agents/<name>.agent.md` | Standard; also `.copilot/agents/` |
+| Plugin | `<plugin>/agents/<name>.agent.md` | Inside plugin root |
+
+The `.agent.md` extension is **mandatory** — Copilot CLI does not pick up plain `.md` files in the `agents/` directory.

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

@@ -0,0 +1,68 @@
+---
+source_keys:
+  - context7-websites-code-claude
+  - claude-code-plugins-docs
+  - claude-code-subagents-docs
+  - context7-github-en-copilot
+  - github-custom-agents-configuration
+  - github-cli-plugin-reference
+  - github-plugins-creating
+---
+
+# Sources
+
+## context7-websites-code-claude
+
+- **URL:** context7:/websites/code_claude
+- **Research doc:** plugins/kyberforge/docs/research/docs/claude-code-plugins/sources.md
+- **Description:** Official Claude Code documentation site indexed by Context7 — plugin manifest schema, subagent definition types, marketplace JSON format, agent markdown file format
+- **Contributing files:** SKILL.md, assets/templates/claude-code.md, references/deployment-modes.md
+- **Status:** `extracted`
+
+## claude-code-plugins-docs
+
+- **URL:** https://code.claude.com/docs/en/plugins
+- **Research doc:** plugins/kyberforge/docs/research/docs/claude-code-plugins/sources.md
+- **Description:** Official Claude Code plugin authoring guide — plugin structure, manifest fields, loading methods, skill namespacing, agent activation, marketplace submission
+- **Contributing files:** SKILL.md, references/deployment-modes.md
+- **Status:** `extracted`
+
+## claude-code-subagents-docs
+
+- **URL:** https://code.claude.com/docs/en/sub-agents
+- **Research doc:** plugins/kyberforge/docs/research/docs/claude-code-plugins/sources.md
+- **Description:** Official Claude Code subagent reference — definition format, all frontmatter fields, scope priority, built-in agents, CLI flags, environment variables, known limitations
+- **Contributing files:** SKILL.md, assets/templates/claude-code.md, references/deployment-modes.md
+- **Status:** `extracted`
+
+## context7-github-en-copilot
+
+- **URL:** context7:/websites/github_en_copilot
+- **Research doc:** plugins/kyberforge/docs/research/docs/github-copilot-plugins/sources.md
+- **Description:** Official GitHub Copilot documentation indexed by Context7; covers CLI plugins, custom agents, SDK, and marketplace
+- **Contributing files:** SKILL.md, assets/templates/copilot.agent.md, references/deployment-modes.md
+- **Status:** `extracted`
+
+## github-custom-agents-configuration
+
+- **URL:** https://docs.github.com/en/copilot/reference/custom-agents-configuration
+- **Research doc:** plugins/kyberforge/docs/research/docs/github-copilot-plugins/sources.md
+- **Description:** Reference for cloud and IDE custom agent definition format — frontmatter fields, tool aliases, MCP server config, secrets interpolation, scoping hierarchy
+- **Contributing files:** SKILL.md, assets/templates/copilot.agent.md, references/deployment-modes.md
+- **Status:** `extracted`
+
+## github-cli-plugin-reference
+
+- **URL:** https://docs.github.com/en/copilot/reference/copilot-cli-reference/cli-plugin-reference
+- **Research doc:** plugins/kyberforge/docs/research/docs/github-copilot-plugins/sources.md
+- **Description:** Full CLI plugin reference — plugin.json schema, marketplace.json schema, all CLI commands and flags, install specification formats, loading precedence, env vars, LSP config
+- **Contributing files:** SKILL.md, scripts/new-agent.sh, references/deployment-modes.md
+- **Status:** `extracted`
+
+## github-plugins-creating
+
+- **URL:** https://docs.github.com/en/copilot/how-tos/copilot-cli/customize-copilot/plugins-creating
+- **Research doc:** plugins/kyberforge/docs/research/docs/github-copilot-plugins/sources.md
+- **Description:** How-to for creating Copilot CLI plugins — plugin structure, agent and skill authoring, hooks format, MCP config, development lifecycle
+- **Contributing files:** SKILL.md, assets/templates/copilot.agent.md
+- **Status:** `extracted`