fix: normalise the OpenShell version pin to a release tag

[vyncint]

Two things, both found by actually running against newer upstreams as asked.

--openshell-version has never worked

OpenShell tags every release vX.Y.Z, and its installer uses OPENSHELL_VERSION verbatim as the tag in the asset URL. So the value our own README documented asked for a release that does not exist:

URL
…/releases/download/0.0.97/openshell.rb	404
…/releases/download/v0.0.97/openshell.rb	200
…/releases/download/0.0.111/openshell.rb	404
…/releases/download/v0.0.111/openshell.rb	200

Reproduced exactly: OPENSHELL_VERSION=0.0.111 died with failed to download …/0.0.111/openshell.rb; the selected release may not include a Homebrew formula, and v0.0.111 installed cleanly. Broken since the flag shipped in v0.2.7 — the documented example never worked.

Both the Go path (update --all --openshell-version) and install.sh --openshell-version now normalise a bare X.Y.Z to vX.Y.Z. An explicit vX.Y.Z passes through, as does OpenShell's documented dev literal.

apple/container needs no such handling — its tags carry no v (1.2.2), and -v 1.2.2 worked as-is.

Compatibility now verified against 0.0.111 / 1.2.2

Live on the reference machine, upgraded from 0.0.97 / 1.2.0:

• setup clean; derived supervisor:0.0.111 and pulled it
• create → Ready → exec → Linux 6.18.15 aarch64, workload as uid 998
• network policy still enforced in-guest (egress 000/blocked)
• restart adoption: agent kickstart → reconciled sandbox record … reason=BackendReady, exec still works
• delete clean

Newer gateways are compatible by design, not luck. The contract gained four RPCs after v0.0.96 — GetGatewayListenerRequirements, StartSandbox, EnsureWorkspace, DeleteWorkspace — and this driver implements none. Three are optional by construction; from crates/openshell-server/src/compute/mod.rs:

Err(status) if status.code() == Code::Unimplemented => Ok(()),

StopSandbox/StartSandbox have no such branch, but are reached only by the new openshell sandbox stop/start commands, or by lifecycle sweeps guarded on gateway_manages_lifecycle — a capability this driver does not advertise, so those sweeps early-return. Confirmed what a user actually sees:

$ openshell sandbox stop full1
Error: × code: 'Operation is not implemented or not supported',
  message: "stop sandbox failed: StopSandbox is not implemented yet"

Clean failure of an unsupported command, nothing damaged. DriverSandboxSpec.command and .tty were also added and are silently ignored.

README, STATUS.md and docs/CONTRACT.md now state this rather than implying the v0.0.96 contract is current, and the release footer advertises the tested range.

Verification

go build, go test -race, golangci-lint (0 issues), shellcheck install.sh, goreleaser check, govulncheck/gosec/gitleaks — all clean. Unit test covers the normaliser including the dev and empty cases.