fix(opencode): define OPENCODE_VERSION in the node server build

[H3XDaemon]

Issue for this PR

Closes #30197

Type of change

• Bug fix
• New feature
• Refactor / code improvement
• Documentation

What does this PR do?

The node server bundle that the desktop app ships as its sidecar is built by script/build-node.ts, which defines OPENCODE_CHANNEL but not OPENCODE_VERSION (the CLI build in script/build.ts defines both). At runtime that global doesn't exist, so InstallationVersion falls back to "local" while InstallationLocal stays false — and config startup pins the plugin dependency install to @opencode-ai/plugin@local, a version that doesn't exist on npm. Every desktop install hits this on every session; #30908 and likely #31708 are the same failure.

It also means anything reading InstallationVersion in the sidecar reports local — session records, telemetry serviceVersion, User-Agent.

One line: add the same OPENCODE_VERSION define the CLI build already uses.

How did you verify your code works?

Built the bundle before and after with OPENCODE_VERSION=1.17.18 OPENCODE_CHANNEL=latest. Before: the bundle still contains the typeof OPENCODE_VERSION === "string" ? OPENCODE_VERSION : "local" fallback (channel is inlined, version is not). After: InstallationVersion = "1.17.18" is inlined and the fallback is gone, so the dependency install resolves @opencode-ai/plugin@1.17.18, which exists on the registry. The @local spec in the reported logs matches this exact path — I hit it on my own machine (see #35986 debugging) where the failed install caused the plugin to resolve to workspace TS sources under node.

Screenshots / recordings

n/a

Checklist

• I have tested my changes locally
• I have not included unrelated changes in this PR