feat: add mise install support

[AndryOre]

Pre-flight Checks

• I have searched existing issues and this is not a duplicate
• I understand this issue needs status:approved before a PR can be opened

Problem Description

engram supports Homebrew, go install, and manual binary downloads, but has no first-class mise install path, and the repo declares no pinned toolchain of its own (contributors reconstruct Go/Node versions by reading go.mod and the CI workflows by hand). Separately, updateInstructions() (internal/version/check.go) only branches on runtime.GOOS, so a user who installed engram via mise is told to run brew upgrade engram or go install .../engram@latest — instructions that ignore (and can conflict with) the install mise already manages.

Proposed Solution

• Add a mise.toml at the repo root pinning go and node to the versions the project already targets, plus a small CI guard script that fails a PR if that pin drifts from go.mod / the CI workflow files (so it can't silently go stale).
• Document installing engram via mise in docs/INSTALLATION.md / README.md (macOS, Linux, and Windows — engram already ships Windows release archives).
• Teach updateInstructions() to detect a mise-managed install and print mise upgrade engram instead of the Homebrew/go install hint in that case; every other install method keeps today's behavior unchanged.

Example:

mise use -g github:Gentleman-Programming/engram@latest
engram version

Companion registry submissions (separate, non-code, tracked outside this repo) are both merged now, so the shorter mise use -g engram@latest form will resolve once mise ships a release with the updated registry:

• feat(Gentleman-Programming/engram): add engram aquaproj/aqua-registry#59476 (merged)
• registry: add engram jdx/mise#12480 (merged)

Affected Area

Other

Alternatives Considered

Leaving mise unsupported and only documenting Homebrew/go install/manual download — but this repo's own CI already needs a pinned Go/Node toolchain that contributors currently have to reconstruct by hand, and the update hint giving wrong advice to mise users is a real (if minor) correctness bug independent of mise adoption.

[AndryOre]

Both external registry streams for this chain are now merged: aquaproj/aqua-registry#59476 and jdx/mise#12480. The github: install command documented in #792 keeps working as-is; the short name (engram@latest) will resolve once mise ships a release after v2026.8.16.

Nothing left blocking on the external side. Whenever you get a chance, this issue still needs status:approved before #790/#791/#792 can merge, and each of those three PRs is still missing its type:* label.

[WilberC]

I'd like to narrow this proposal to a small documentation-only update in docs/INSTALLATION.md.

The main goal is discoverability: Engram already supports installation through mise, but this supported option is not clearly documented. The guide should add the mise installation command and briefly distinguish the stable v1 latest channel from the v2 release-candidate channel (v2.0.0-rc.10) until v2 reaches a stable release.

No code, README, toolchain, or runtime changes are needed for this scope. I'd appreciate maintainer feedback on whether this focused documentation update would be useful.

[AndryOre]

Thanks for picking this up. Worth separating two halves, because one already landed.

The channel distinction is on main already. #1042 (Sept 6) added "Choose a release channel before installing" to docs/INSTALLATION.md, split both go install paths into v1 and v2 lines, and linked RELEASE-POLICY.md.

The mise path is what's still missing, and it can't carry a v2 RC channel. Checked against mise 2026.9.5 today:

mise latest engram                                   → 1.20.0
mise ls-remote engram                                → tops out at 1.20.0, no rc tags
mise ls-remote github:Gentleman-Programming/engram   → same

Both backends filter semver prereleases, so engram@latest resolves to stable v1.20.0 and there is no v2 channel to point at. Documenting one would describe a command that doesn't resolve. What I added instead, in the rebase below, is an explicit note in that section saying mise tracks the stable v1 line and that v2 release candidates aren't published to the mise registry yet. That answers the same confusion accurately.

Small correction on the premise: mise support isn't pre-existing, it came out of this issue. aquaproj/aqua-registry#59476 and jdx/mise#12480 shipped in mise v2026.9.0, which is why the short name resolves at all.

On narrowing the scope: #790 (toolchain pins, CI drift guard) is fine to drop, it's repo-internal with no user-facing benefit. #791 I'd keep, since a mise-installed engram currently prints a brew upgrade hint, and docs alone leave that wrong advice in the binary.

#792 is now rebased onto current main as a single commit, sitting on the new INSTALLATION.md structure and with the release-channel note added. Happy to land it alone first if that's the order you prefer.