README: install with Homebrew

[krishhgg]

PR 4 of 4 for packaging. PRs 1 to 3 (#34, #35, #36) are merged, so this targets main. It puts installation at the top of the README.

What changed

• Install comes first. A new ## Install section sits right after the badges. It covers:
  • brew install krishhgg/tap/sys1rust and sys1rust serve
  • the 846 MB first-start download, pull and models
  • brew services start sys1rust and its log path
  • which bundle Homebrew picks: the macOS 26.2 build is about 3x faster on the M5, 1357 ms against 4155 ms summed p50
  • tarballs without Homebrew: the quarantine flag, keeping bin/ and lib/ together, and putting bin/ on PATH or symlinking the binary
• No second server. Try it uses whichever server is already running. The README says to stop a foreground server with Ctrl-C before brew services start, since both use port 8000.
• Build from source moves to its own section before ## More. It needs Rust 1.89 or newer, and the "no release yet" lines are gone.
• Options now points to sys1rust serve --help.
• answer_confidence is described per answer type. For choice it is the chosen label's probability, for score the most likely level's, and for noul the larger of yes and no. This matches decode_answers.
• Wording. Writing-rule fixes across the README: digits, active voice, no connecting colons.

Not live yet

The brew install command works once v0.1.0 is published. That release follows packaging/RELEASE.md, starting with an rc tag.

Checks

• Every in-page link (#install, #speed, #models, #build-from-source) matches a heading, and every file link exists.
• The landing view at 1375x893 still shows the title, chart, intro, link row and badges above the fold, with Install right below.
• A symlinked bin/sys1rust from an unpacked bundle runs and finds its lib/.

🤖 Generated with Claude Code

Confidence Score: 5/5

The PR appears safe to merge.

Summary

The PR puts Homebrew installation first and moves source-build steps into their own section.

• Covers background serving, release tarballs, and bundle requirements.
• Clarifies what answer_confidence means for each answer type.
• The latest change fixes the source-build path instructions. No new issues were found.

_{Reviews (2) · Last reviewed commit: "Tell source builders how to run sys1rust..."}