feat(skill): add @tsops/skill — Claude Skill for tsops

[Pom4H]

Ships the canonical Skill content at skills/tsops/ and a thin npm
package (@tsops/skill) that installs it into ~/.claude/skills/tsops or
./.claude/skills/tsops. After install, Claude Code, the Agent SDK, and
any other tool implementing the Agent Skills standard load the Skill
automatically when relevant.

Why a Skill, not just docs: the docs explain what tsops is. The Skill
tells an agent how to operate it without violating the load-bearing
rules — no internal URLs in env vars, always run tsops plan before
deploy, always tsc --noEmit after a rename, never --no-verify past
secret validation. Without the Skill, an LLM agent reaches for
BACKEND_URL=http://api:3000 because that pattern is everywhere else
on the public internet. With it, it reaches for config.url('api', 'service').

Distribution model (mirrors workflows-sdk.dev structure):

• canonical source on GitHub at skills/tsops/
• npm package @tsops/skill that installs the Skill via npx @tsops/skill install
• docs page at docs/guide/skill.md

Skill structure:
skills/tsops/
├── SKILL.md entry point — frontmatter + hard rules
├── reference/
│ ├── commands.md CLI flags
│ ├── runtime-helpers.md config.url / config.env / config.dns
│ ├── secrets.md secret validation, cluster fallback
│ └── preview-overlays.md overlay namespace lifecycle
└── examples/
├── add-app.md recipe
├── rename-app.md recipe — compiler-driven rename
└── add-secret.md recipe

Package structure (packages/skill/):

• bin/install.mjs — tsops-skill install [--user|--project] [--force],
  plus uninstall and where subcommands
• scripts/sync-skill.mjs — build step that copies skills/tsops/ into
  packages/skill/skill/ for the npm tarball
  (npm doesn't preserve symlinks reliably)
• README.md — install + verify + uninstall instructions

This PR is strictly additive — no existing files are modified, so no
conflict with the in-flight docs refresh in PR #51.

Follow-ups (separate small PRs after both merge):

• surface /guide/skill in the docs sidebar
• add a "Use with Claude" link from the main README
• submit to anthropics/skills community registry if/when accepted