feat: add repo planning/binary repo support and Meson build integration

- add repos.toml source/binary repo configuration with arch overrides and priorities
- add dependency planner/execution plan flow with interactive provider selection and --yes support
- expand binary repo DB metadata (sha512, dependencies, file lists) and repo owns/search helpers
- add rootfs-scoped fd locking and minisign detached signing/verification helpers
- add Meson build/test support for the project with builddir-local CARGO_HOME/CARGO_TARGET_DIR
- install contrib example configs into sysconfdir (/etc/depot.d layout) via Meson
- improve builder env handling (sanitized PATH, tool env passthrough, CXXFLAGS support)
- support += appends in package specs and add build.flags.cxxflags parsing
- prompt for git credentials when private repo auth is required
- update docs/examples and dependency setup (system libs, zstdmt, tempfile pin)

src/deps.rs

@@ -78,6 +78,11 @@ fn parse_dep(dep: &str) -> ParsedDep<'_> {
     }
 }
 
+/// Return the dependency name portion without any version/operator suffix.
+pub fn dep_name(dep: &str) -> &str {
+    parse_dep(dep).name
+}
+
 /// Compare two version strings using semver if possible, fallback to string compare
 fn compare_versions(installed: &str, required: &str, op: VersionOp) -> bool {
     // Try semver comparison first
@@ -134,6 +139,17 @@ fn is_dep_satisfied(
     }
 }
 
+/// Check whether a dependency expression is satisfied by the installed package DB.
+pub fn is_dep_satisfied_in_db(dep: &str, db_path: &Path) -> Result<bool> {
+    if !db_path.exists() {
+        return Ok(false);
+    }
+
+    let installed = db::get_installed_packages(db_path)?;
+    let provides = db::get_all_provides(db_path)?;
+    is_dep_satisfied(dep, &installed, &provides, db_path)
+}
+
 /// Check if all build dependencies are satisfied
 pub fn check_build_deps(spec: &PackageSpec, db_path: &Path) -> Result<Vec<String>> {
     let mut missing = Vec::new();