fix: harden embedded Postgres install and recovery on Linux

[rabsef-bicrym]

What

This PR fixes Volt startup failures on Arch Linux by hardening embedded Postgres installation and recovery. It resolves broken shared-library link states that could cause initdb to fail with missing library errors.

Why

Issue #7 reports a startup crash on Arch with shared library load failures during embedded Postgres initialization. The install path could accept broken library link states as valid and then repeatedly fail on subsequent launches.

Changes

• Preserve library symlink targets during extraction copy
• Validate embedded Postgres binaries and core libs
• Auto-repair invalid installs via clean re-download
• Add clearer shared-library failure remediation guidance

Testing

• bun run --cwd packages/voltcode typecheck
• Arch Linux Docker end-to-end startup validation
• Arch Linux Docker corruption-repair validation

Closes #7.

[thelifeandtimes]

This is still broken. running the install script from the v0.6.1 release gets:

While building from source still has messed up dist/ directory locations and wonky architecture->path generation:

volt fix/issue-7-arch-embedded-postgres ❯ cp dist/voltcode-$(uname -s | tr '[:upper:]' '[:lower:]')-$(uname -m | sed 's/aarch64/arm64/')/bin/volt ~/.voltcode/bin/volt
cp: cannot stat 'dist/voltcode-linux-x86_64/bin/volt': No such file or directory

Fixing that still errors out when running the locally built binary as well:

albeit with a slightly different error.