fix cross-repo path deps; remove el compiler from neuron-lang/

- neuron-runtime, neuron-store, neuron-migrate: fix path deps
  (products/engram/ → foundation/engram/engrams/, products/el/ → foundation/el/engrams/)
- neuron-rs workspace: fix axon-events/axon-protocol paths
  (../../../platform/ → ../../platform/, paths were off by one level)
- neuron-lang/compiler/ removed (el self-hosting compiler now lives in foundation/el/el-compiler/)

neuron-lang/config.el

@@ -0,0 +1,86 @@
+// config.el — Runtime configuration subsystem.
+//
+// Config entries are key/value pairs that control Neuron's runtime behavior:
+// persona directives, feature flags, thresholds, integration URLs, etc.
+//
+// WHY sealed blocks?
+// Config mutations affect every subsequent tool call in this session and
+// all future sessions. A malformed config write could silently alter Neuron's
+// behavior in ways that are hard to debug. Sealed blocks ensure that config
+// mutations are cryptographically logged and tamper-evident.
+//
+// The live config is authoritative over CLAUDE.md. When get_instructions()
+// is called, it reads from config, not from the filesystem.
+//
+// inspect_config is a @public read — config keys are not secrets themselves.
+// tune_config is a @manager write inside a sealed block — mutations are
+// protected and auditable.
+
+from types import {
+    ConfigEntry,
+    NeuronError,
+}
+
+// ── Public API ────────────────────────────────────────────────────────────────
+
+// inspect_config — read one or all config entries.
+//
+// When key is empty string, returns all config entries.
+// When key is provided, returns just that entry.
+// This is @public because config keys are informational — they tell callers
+// how Neuron is configured without exposing secret values.
+@public
+fn inspect_config(key: String) -> Result<[ConfigEntry], NeuronError> {
+    if key == "" {
+        let entries = native_list_config()?
+        return Ok(entries)
+    }
+    let value = native_get_config(key)?
+    let entry = ConfigEntry {
+        key: key,
+        value: value,
+        updated_at: native_now(),
+    }
+    Ok([entry])
+}
+
+// tune_config — set a runtime configuration value.
+//
+// Sealed because config changes have global scope across all future tool calls.
+// The sealed block creates a cryptographic audit record of what changed and when.
+//
+// Key naming convention: "neuron.<subsystem>.<setting>"
+// Examples:
+//   neuron.persona.directives
+//   neuron.memory.importance_threshold
+//   neuron.session.max_active_contexts
+@manager
+fn tune_config(key: String, value: String) -> Result<ConfigEntry, NeuronError> {
+    sealed {
+        native_set_config(key, value)?
+        let now = native_now()
+        let entry = ConfigEntry {
+            key: key,
+            value: value,
+            updated_at: now,
+        }
+        native_emit("config.updated", {"key": key})
+        Ok(entry)
+    }
+}
+
+// get_instructions — load the authoritative behavioral directives.
+//
+// This is the canonical way to load Neuron's behavioral configuration.
+// Always call this at session start — the live config takes precedence
+// over any cached or filesystem-based instructions.
+@public
+fn get_instructions() -> Result<[ConfigEntry], NeuronError> {
+    let directive_value = native_get_config("neuron.persona.directives")?
+    let entry = ConfigEntry {
+        key: "neuron.persona.directives",
+        value: directive_value,
+        updated_at: native_now(),
+    }
+    Ok([entry])
+}