[M5+] add resolver::devbox_resolve (search.devbox.sh)

CHANGELOG.md

@@ -78,6 +78,19 @@ All notable changes to cargoxx will be documented in this file.
   and `[build]` honoring `warnings_as_errors` and `sanitizers`. Source
   paths emitted relative to `build/` (i.e. prefixed with `../`).
   Output is deterministic. `tests/codegen_cmake.cpp` covers 11 cases.
+- `cargoxx.resolver::devbox_resolve(name, version)` and pure parser
+  `parse_devbox_resolve(json)` — port of devbox's
+  `internal/searcher/client.go` Resolve method. Hits
+  `https://search.devbox.sh/v1/resolve?name=<n>&version=<v>` via curl
+  and pulls out `name`, `version`, `commit_hash`, `attr_paths`. Falls
+  back to the per-system `systems.<plat>.commit_hash` when the
+  top-level field is empty (older response shapes). 404 →
+  `ResolutionUnknownPackage`, missing commit_hash →
+  `ResolutionVersionNotFound`, transport / parse errors →
+  `ResolutionNetworkError`. `tests/devbox_resolve_parse.cpp` covers
+  6 cases against fixtures derived from a real fmt 10.2.1 response;
+  `tests/devbox_resolve_live.cpp` (gated by `CARGOXX_NETWORK_TESTS=1`)
+  hits the live API.
 - `cargoxx add <pkg>` now auto-resolves packages outside the curated
   linkdb. On `LinkdbUnknownPackage`, `cmd_add` invokes
   `resolver::discover` which: probes `nixpkgs#<pkg>` to confirm the