fix: address review comments on skill refactor

[pjcdawkins]

Stacked on #14 (refactor-skills). Addresses review comments on the skill refactor.

Summary

• SKILL.md frontmatter. allowed-tools now uses comma separation so the read-only patterns parse as separate entries instead of one big invalid spec. Pattern shapes kept narrow and read-only.
• Deploy strategy default. upsun push / upsun deploy default to stopstart, not rolling. Flipped the description; rolling is now described as opt-in for zero-downtime deploys.
• `env:deploy:type` syntax. Was shown as a property set via `set env:deploy:type manual`; actual syntax is `upsun env:deploy:type manual` (it's a subcommand).
• Resources guidance. Clarified that `upsun resources:set --size` takes numeric CPU values (e.g. `myapp:0.25`); container profiles (`HIGH_CPU` etc.) are still correct but live in `.upsun/config.yaml` as `container_profile:`, not on the CLI.
• MCP tool names. Qualified `list-project` / `list-environment` with the `mcp__upsun__` prefix so agents invoke them correctly.
• Install paths. Updated to `github.com/upsun/cli` (CLI repo moved from `platformsh/cli`); tap is `upsun/tap`, Scoop bucket is `upsun/homebrew-tap`. Mentioned native Alpine/Debian/RPM packages. Applied the same updates to `README.md` and the CI workflow.
• README cleanup. Replaced stale `using-upsun` references with `upsun`; collapsed the eleven-file reference list to the single `config.md` that ships with the new skill; switched `auth:browser-login` to `upsun login`.
• CI workflow. Renamed the skill install step; dropped the redundant `$HOME/.platformsh/bin` PATH export (the installer uses `$HOME/.local/bin`, which is already on PATH for the ubuntu-latest runner).