feat: Linux multi-arch OpenCode container support

[extreme4all]

fixes #9246, this is a suggestion for implementation

What this change does:
This PR updates the OpenCode Dockerfile to support Linux containers with both musl and glibc binaries for x64 and arm64 architectures, enabling multi-distro builds beyond Alpine.

Specifically, the new Dockerfile now supports:

Architecture	libc / variant	Base image	Stage / Binary
x64	musl	alpine	build-x64-musl
x64	glibc	debian	build-x64-glibc
x64	baseline (AVX2 fallback)	debian	build-x64-baseline
arm64	musl	alpine	build-arm64-musl
arm64	glibc	debian	build-arm64-glibc

this probably needs some more work to build the images to the registery and for testing
I HAVE NOT DONE ANY TESTING, since i can't build for all arches and i don't know how to get the dist/

[github-actions]

Hey! Your PR title #9246 Enhancement: Linux multi-arch OpenCode container support doesn't follow conventional commit format.

Please update it to start with one of:

• feat: or feat(scope): new feature
• fix: or fix(scope): bug fix
• docs: or docs(scope): documentation changes
• chore: or chore(scope): maintenance tasks
• refactor: or refactor(scope): code refactoring
• test: or test(scope): adding or updating tests

Where scope is the package name (e.g., app, desktop, opencode).

See CONTRIBUTING.md for details.

[github-actions]

The following comment was made by an LLM, it may be inaccurate:

No duplicate PRs found

[github-actions]

Thanks for your contribution!

This PR doesn't have a linked issue. All PRs must reference an existing issue.

Please:

1. Open an issue describing the bug/feature (if one doesn't exist)
2. Add Fixes #<number> or Closes #<number> to this PR description

See CONTRIBUTING.md for details.