feat(kyberforge): add plugin-author and marketplace-author skills

## Why

Plugin and marketplace management had no governed authoring path. Creating or
updating a plugin required knowing the dual-manifest convention, version parity
rules, and directory skeleton by memory — nothing enforced consistency or guided
the process.

`/plugin-author` closes that gap by owning the full plugin scaffold lifecycle:
create, update, rename, and release. `/marketplace-author` handles the
marketplace-facing side: register, deregister, and update plugin entries in
`marketplace.json`.

ADR-0016 codifies the version parity convention (identical `version` in both
`plugin.json` and `.claude-plugin/plugin.json`) that `/plugin-author` now
enforces. The two plugin.json files in this repo are backfilled to comply
(keys also sorted to pass the pretty-format-json hook). CONTEXT.md gains
glossary entries for "plugin scaffold" and "version parity" so future agents
have shared vocabulary for these concepts.

## Implementation Notes

`/plugin-author` ships a `scripts/new-plugin.sh` scaffold script that generates
the directory skeleton and both manifests in one shot; the skill calls the script
rather than generating files ad hoc so the scaffold is reviewable and repeatable.

Version parity is an invariant, not a suggestion — the skill will fail loudly
on create/update if the two versions would diverge.

ADR: docs/adr/0016-plugin-version-parity.md

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

@@ -0,0 +1,50 @@
+---
+source_keys:
+  - context7-websites-code-claude
+  - claude-code-plugins-docs
+  - github-cli-plugin-reference
+  - github-plugins-creating
+  - github-plugins-finding-installing
+---
+
+# 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, marketplace JSON format, `claude plugin` CLI commands, validation, tagging
+- **Contributing files:** SKILL.md, references/manifest-fields.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, CC manifest fields (`displayName`, `author.url`, `version`, `outputStyles`, `experimental`), marketplace submission, `claude plugin tag`
+- **Contributing files:** SKILL.md, references/manifest-fields.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 Copilot CLI plugin reference — `plugin.json` schema (all fields, types, constraints), marketplace.json schema, CLI commands, manifest lookup order
+- **Contributing files:** SKILL.md, scripts/new-plugin.sh, references/manifest-fields.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, Copilot manifest fields, development lifecycle, hooks format, MCP config
+- **Contributing files:** SKILL.md, scripts/new-plugin.sh
+- **Status:** `extracted`
+
+## github-plugins-finding-installing
+
+- **URL:** https://docs.github.com/en/copilot/how-tos/copilot-cli/customize-copilot/plugins-finding-and-installing
+- **Research doc:** plugins/kyberforge/docs/research/docs/github-copilot-plugins/sources.md
+- **Description:** Finding and installing Copilot CLI plugins — install spec formats, marketplace registration, `copilot plugin` CLI commands
+- **Contributing files:** SKILL.md
+- **Status:** `extracted`