deps phase 2: jolt-deps tool resolves deps.edn git/local deps

A separate jolt-deps executable (mirroring jpm beside janet) resolves a
deps.edn into source roots and runs jolt with them on JOLT_PATH; the runtime
stays deps-agnostic.

- src/jolt/deps.janet: read deps.edn (Janet parses it directly), resolve
  :git/* and :local/root via jpm/pm's download-bundle (git fetch + cache, no
  build), recurse for transitive deps, return de-duped roots. jpm loaded
  lazily so it's never embedded. Roots cached on a deps.edn hash.
- src/jolt/deps_cli.janet + project.janet: the jolt-deps tool — path/run/repl/-e.
- main: apply JOLT_PATH at runtime (the CLI ctx is frozen into the image at
  build, so init's env read wouldn't see it).

Verified end to end against a local dep and a real git dep (medley). git only,
pure clj/cljc. Test: deps-resolve-test (local deps, no network).

project.janet

@@ -8,3 +8,9 @@
 (declare-executable
   :name "jolt"
   :entry "src/jolt/main.janet")
+
+# Separate tool (like jpm beside janet): resolves deps.edn into Jolt source
+# roots. The jolt runtime stays deps-agnostic — it just reads JOLT_PATH.
+(declare-executable
+  :name "jolt-deps"
+  :entry "src/jolt/deps_cli.janet")