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/bin/plugin.json

@@ -1,9 +1,15 @@
 {
-  "name": "bin",
-  "description": "A place for things to be binned",
-  "author": { "name": "Defame1297", "email": "defame1297@rkdr.net" },
-  "license": "MIT",
-  "keywords": [],
   "agents": "agents/",
-  "skills": ["skills/"]
+  "author": {
+    "email": "defame1297@rkdr.net",
+    "name": "Defame1297"
+  },
+  "description": "A place for things to be binned",
+  "keywords": [],
+  "license": "MIT",
+  "name": "bin",
+  "skills": [
+    "skills/"
+  ],
+  "version": "1.0.1"
 }