Fix 4 test failures from Proxmox VM report

1. converter panic (5 unit tests): "FIXME_CHECKSUM".repeat(4) is only
   56 chars but was sliced to [..64], causing index-out-of-bounds panic.
   Both crux.rs and gentoo.rs converters now use "a".repeat(64) as the
   placeholder checksum instead.

2. dpack list/check exit code 1: these commands call PackageDb::open()
   which tries to create /var/lib/dpack/db — fails without root.
   Test runner now creates a temp dpack.conf pointing at a writable
   temp directory with repos symlinked from the project. Also added
   search and info smoke tests.

3. host.ovmf: not a code bug — edk2-ovmf just needs to be installed
   on the test VM (sudo pacman -S edk2-ovmf --noconfirm).

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

src/dpack/src/converter/crux.rs

@@ -119,7 +119,7 @@ pub fn parse_pkgfile(content: &str) -> Result<PackageDefinition> {
         },
         source: SourceInfo {
             url: template_url,
-            sha256: "FIXME_CHECKSUM".repeat(4)[..64].to_string(), // Placeholder
+            sha256: "a".repeat(64), // Placeholder
             git: String::new(),
             branch: String::new(),
             tag: String::new(),

src/dpack/src/converter/gentoo.rs

@@ -139,7 +139,7 @@ pub fn parse_ebuild(content: &str, filename: &str) -> Result<PackageDefinition>
         },
         source: SourceInfo {
             url: source_url,
-            sha256: "FIXME_CHECKSUM".repeat(4)[..64].to_string(),
+            sha256: "a".repeat(64),
             git: String::new(),
             branch: String::new(),
             tag: String::new(),