refactor: move lancedb skill to a codex/claude plugin (#3681)

Moves the skill from .agents/skills/lancedb to
plugins/lancedb/skills/lancedb, as recommended by codex and claude.

Install path now is:
### Codex/ChatGPT app
Codex: Plugins -> "Create" arrow -> Add plugin marketplace
search for lancedb plugin and install
### Codex CLI
```
codex plugin marketplace add lancedb/lancedb
codex plugin install lancedb@lancedb # name@marketplace
```
### Claude app
Settings -> Plugins -> Add -> Add marketplace
search for lancedb plugin and install
### Claude CLI
```
claude plugin marketplace add lancedb/lancedb
claude plugin install lancedb@lancedb
```
Here's how it looks on ChatGPT/Codex app:
(the main icon has light and dark modes; the smaller one on the skill
doesn't so I made it gray 🤷 )
<img width="764" height="560" alt="Screenshot 2026-07-16 at 2 49 24 PM"
src="https://github.com/user-attachments/assets/b82cda16-3392-4740-ac47-b2f187cb2655"
/>

plugins/lancedb/.codex-plugin/plugin.json

@@ -0,0 +1,33 @@
+{
+  "name": "lancedb",
+  "version": "0.1.0",
+  "description": "Codex plugin for building LanceDB pipelines in Python and TypeScript.",
+  "author": {
+    "name": "LanceDB"
+  },
+  "keywords": [
+    "lancedb",
+    "vector-search",
+    "full-text-search",
+    "hybrid-search",
+    "python",
+    "typescript",
+    "pipelines"
+  ],
+  "skills": "./skills/",
+  "interface": {
+    "displayName": "LanceDB",
+    "shortDescription": "Build LanceDB pipelines in Python and TypeScript.",
+    "longDescription": "Write, review, debug, and document LanceDB pipelines in Python and TypeScript that work across local LanceDB OSS tables and remote LanceDB Enterprise/Cloud tables, with idiomatic query/search patterns and performance defaults for ingestion, indexing, filtering, and diagnostics.",
+    "developerName": "LanceDB",
+    "websiteURL": "https://www.lancedb.com",
+    "category": "Developer Tools",
+    "capabilities": [
+      "Developer Tools"
+    ],
+    "defaultPrompt": "Create a LanceDB table, embed sample text, and run a vector search.",
+    "composerIcon": "./assets/logo.png",
+    "logo": "./assets/logo.png",
+    "logoDark": "./assets/logo-dark.png"
+  }
+}