feat(install): publish homebrew cask to hmk/tap on each release

[hmk]

Summary

Wires up Homebrew distribution via `hmk/homebrew-tap`. After merge + a release, users can install with:

```bash
brew install hmk/tap/try-bedazzled
```

Changes

• `.goreleaser.yaml` — `homebrew_casks` block (current goreleaser; `brews` is deprecated). Pushes a Cask formula to `hmk/homebrew-tap` on each release using `HOMEBREW_TAP_TOKEN` (fine-grained PAT, Contents:write on the tap repo only).
• `release.yml` — passes `HOMEBREW_TAP_TOKEN` through to the goreleaser step. Same `release` environment as the signing secrets.
• README — install section now leads with `brew install`, with the install script as the cross-platform fallback.
• INSTALL.md — Homebrew section added at the top.

Why this shape

• Generic tap (`hmk/homebrew-tap`) over per-tool tap: install path becomes `hmk/tap/try-bedazzled` instead of `hmk/try-bedazzled/try-bedazzled`. Leaves room for sibling tools.
• Cask, not formula: goreleaser's `brews` block is deprecated; `homebrew_casks` is the supported path. Casks work fine for CLIs.
• Caveats block: brew doesn't edit shell rc files, so the cask prints the `eval "$(try init)"` snippet on install.

Test plan

• Merge → release-please opens 0.3.0 PR (this is a `feat:`) → merge that → goreleaser publishes the release AND pushes a Cask file to `hmk/homebrew-tap`
• On a fresh shell: `brew install hmk/tap/try-bedazzled` succeeds
• `brew info try-bedazzled` shows the caveats with the shell snippet
• `try --version` reports the installed version
• `brew upgrade try-bedazzled` works on subsequent releases

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