Restructure as a self-contained Agent Skills package (fix Codex install)

Move the skill into skills/watch/ so SKILL.md and its scripts/ runtime are
siblings inside one folder. `npx skills add` (Codex/Cursor/Copilot/agents) now
copies a working skill as a unit; previously it grabbed the root SKILL.md alone
and left scripts/ behind, so the skill was dead on arrival on every non-Claude
host. Mirrors the layout last30days-skill adopted for the same reason.

- skills/watch/{SKILL.md,scripts/}: self-contained skill folder
- SKILL.md: resolve a harness-agnostic $SKILL_DIR (the dir it was Read from)
  instead of the Claude-Code-only ${CLAUDE_SKILL_DIR}; guard + 19 call sites
- drop commands/watch.md: /watch derives from frontmatter (name + user-invocable)
- .codex-plugin/plugin.json: full manifest with "skills": "./skills/" + interface
- add .agents/plugins/marketplace.json, AGENTS.md, CLAUDE.md, .skillignore
- build-skill.sh: archive the skills/watch subtree (one SKILL.md, no zip -d)
- fix paths in tests, hooks hint, .gitattributes, release.yml
- relocate dev-sync.sh to repo root and fix REPO_ROOT
- README: content-ideas structure, npx skills install, star history

Verified: 37/37 tests pass; npx skills add bundles the full scripts/ runtime;
manifests valid; versions synced at 0.1.3.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

.codex-plugin/plugin.json

@@ -1,3 +1,43 @@
 {
-  "name": "watch"
+  "name": "watch",
+  "version": "0.1.3",
+  "description": "Let Claude watch a video. Downloads with yt-dlp, extracts auto-scaled frames with ffmpeg, pulls captions or falls back to Whisper, and hands frames + transcript to Claude so it can answer questions about the video.",
+  "author": {
+    "name": "Bradley Bonanno"
+  },
+  "homepage": "https://github.com/bradautomates/claude-video",
+  "repository": "https://github.com/bradautomates/claude-video",
+  "license": "MIT",
+  "keywords": [
+    "video",
+    "watch",
+    "youtube",
+    "vimeo",
+    "tiktok",
+    "transcription",
+    "whisper",
+    "yt-dlp",
+    "ffmpeg",
+    "multimodal",
+    "frames"
+  ],
+  "skills": "./skills/",
+  "interface": {
+    "displayName": "watch",
+    "shortDescription": "Give Claude a video input — paste a URL or path and ask about it.",
+    "longDescription": "watch adds a skill that lets the agent watch any video: it downloads with yt-dlp, extracts auto-scaled frames with ffmpeg, pulls a timestamped transcript from native captions (or the Whisper API as a fallback), and hands frames + transcript to the model so it can answer questions grounded in what's actually on screen and in the audio.",
+    "developerName": "Bradley Bonanno",
+    "category": "Productivity",
+    "capabilities": [
+      "Interactive",
+      "Read"
+    ],
+    "websiteURL": "https://github.com/bradautomates/claude-video",
+    "defaultPrompt": [
+      "/watch https://youtu.be/dQw4w9WgXcQ what happens at the 30 second mark?",
+      "/watch ~/Movies/screen-recording.mp4 when does the UI break?",
+      "/watch https://youtu.be/<long-talk> summarize this"
+    ],
+    "brandColor": "#E11D48"
+  }
 }