add epm — El Package Manager

Introduces epm/, a new component written entirely in native El.
epm manages vessels (El's deployable package format): publish to Engram,
install with full dependency resolution, list registry contents, and
inspect vessel metadata.

- epm/manifest.el         — package manifest
- epm/src/manifest.el     — vessel/package manifest parser (line-by-line,
                            same approach as elb.el)
- epm/src/registry.el     — Engram-backed vessel registry (POST /api/nodes,
                            GET /api/search); vessels stored as Entity nodes
                            with label "vessel:<name>:<version>"
- epm/src/install.el      — topological dependency resolver with cycle
                            detection; installs to .epm/vessels/<name>/
- epm/src/epm.el          — main entry point: publish / install / list / info

epm/manifest.el

@@ -0,0 +1,17 @@
+// epm — El Package Manager
+//
+// Manages vessels: publish, install, resolve dependencies.
+// Vessels are stored in Engram as nodes. epm reads the local manifest.el,
+// talks to Engram over HTTP, and writes installed vessels to .epm/vessels/.
+
+package "epm" {
+    version "0.1.0"
+    description "El Package Manager — vessel registry, publish, install, resolve"
+    authors ["Will Anderson <will@neurontechnologies.ai>"]
+    edition "2026"
+}
+
+build {
+    entry "src/epm.el"
+    output "dist/"
+}