feat: add edge prerelease channel and start stable at 0.1.0 (PROT-40)

[BlakeHastings]

Summary

Adds a rolling edge prerelease channel and fixes the initial stable version. protostar now ships on two tracks, matching how Claude Code, rustup, and GoReleaser-based CLIs do it.

Jira: PROT-40

Track	Trigger	Version (MinVer)	Release	Install
stable	merge the release-please Release PR	0.1.0	vX.Y.Z, normal release (releases/latest)	--channel stable (default)
edge	every code change to main	0.1.0-alpha.0.N	moving edge tag, prerelease, assets replaced	--channel edge

What's in here

1. Edge channel — .github/workflows/edge.yml

• Triggers on push to main, path-filtered to src/**, **/*.csproj, Directory.Build.props, and the workflow itself (docs/CI-only merges don't rebuild).
• Builds the 4-platform matrix, then one job re-points the edge tag at the new commit and replaces the prerelease's assets via the gh CLI (no new third-party actions). Delete + recreate keeps the download URLs stable (releases/download/edge/<asset>).
• concurrency: edge with cancel-in-progress so overlapping merges don't fight over the release.
• Actions pinned to commit SHAs (same standard as PR ci: pin workflow actions to commit SHAs (PROT-39) #3).

2. Installer channel selection — scripts/install.{sh,ps1}

• New --channel stable|edge (sh) / -Channel stable|edge (ps1), default stable. stable pulls releases/latest, edge pulls releases/download/edge. Same asset names, so only the URL differs.

3. Initial stable version fix

• release-please defaults a project's first release to 1.0.0 (it ignores pre-major options when the manifest is 0.0.0 — their issue #2087). We're pre-1.0. Setting the manifest + version.txt to 0.0.1 and adding bump-minor-pre-major makes the first release compute as 0.1.0, and keeps future breaking changes inside 0.x.

Why it composes

The edge tag doesn't start with v, so MinVer ignores it — the edge channel can't perturb stable version computation, and release-please only manages its own v* tags. No collisions.

Side effects after merge

• The open release-please Release PR (currently "release 1.0.0") will recompute to 0.1.0.
• Because the edge build is path-filtered to code, a release-please Release-PR merge (which only touches version.txt/CHANGELOG/manifest) won't trigger an edge rebuild.

Verify

dotnet run --project src/Protostar.Cli -- --version   # untagged main -> 0.1.0-alpha.0.N (the edge version)
sh -n scripts/install.sh                              # installer parses

🤖 Generated with Claude Code