v0.18.0: MCP entity-graph CRUD, lifecycle validation, curl -o /dev/null fix

- create_entity, set_entity_state, end_relationship MCP tools
- update_entity_attributes now triggers check derivation via EnsureEntityChecks
- shared db.EnsureEntityChecks + db.ValidateTransition hooks (HTTP + MCP parity)
- curl -o /dev/null now classified read_only (was config_mutation)
- db.ErrTransitionInvalid sentinel for HTTP error-type accuracy
- SOUL.md: capability escalation, self-grounding, exploration budget rules
- Runbook: oikos check lifecycle for agent self-knowledge

internal/policy/command.go

@@ -105,6 +105,15 @@ var curlLeadRe = regexp.MustCompile(`(?i)^curl\b`)
 // When any of these appears, the curl command is no longer read-only.
 var curlMutateRe = regexp.MustCompile(`(?i)(?:^|\s)-X\s+(?:post|put|delete|patch|connect|trace)\b|(?:^|\s)-(?:d|F|T|o)\b|(?:^|\s)--(?:data[-a-z]*|request|form|upload-file|output)\b`)
 
+// curlDevNullOutRe matches curl output redirected to /dev/null in any of curl's
+// argument forms (space, =, or attached). /dev/null is a no-op sink, so a GET
+// that discards its body — the canonical reachability idiom
+// `curl -o /dev/null -w '%{http_code}' URL` — is read-only. Output to any real
+// path (-o /tmp/x) stays a potential mutation. Stripped before curlMutateRe so
+// the remaining flags (-X, -d, ...) still classify correctly: a
+// `curl -o /dev/null -X POST` stays config_mutation.
+var curlDevNullOutRe = regexp.MustCompile(`(?i)(^|\s)-o\s*/dev/null(\s|$)|(^|\s)--output[=\s]\s*/dev/null(\s|$)`)
+
 // redirectOutRe matches shell output redirection to a file (> or >> followed
 // by a path), but excludes the file-descriptor merge form `>&<digit>` (e.g.
 // `2>&1`) which only rearranges streams and writes nothing to disk. RE2 has
@@ -308,6 +317,10 @@ func curlIsReadOnly(curlCmd string) bool {
 	if !curlLeadRe.MatchString(curlCmd) {
 		return false
 	}
+	// -o /dev/null is a no-op sink: strip it before flag detection so the
+	// canonical GET-and-discard reachability probe stays read-only.
+	// A `curl -o /dev/null -X POST` still fails curlMutateRe after stripping.
+	curlCmd = curlDevNullOutRe.ReplaceAllString(curlCmd, " ")
 	if curlMutateRe.MatchString(curlCmd) {
 		return false
 	}