feat: client sync core — config, pull, inventory, manifest, OpenCode target

- admin-protected client config (flag > AGENT_LIB_CONFIG > platform default),
  token used for basic auth only, redacted from all errors and files
- work-repo pull via go-git (bare cache clone + fetch, remote re-pointed on
  config change), clean failure keeps previous state
- inventory: own items + external areas from lockfile; MCP inventoried but
  never deployed
- manifest v1 records name/type/origin/revision/content-hash per item,
  deterministic bytes; folder hashes over sorted relpath+filehash lines so
  tree and disk hashes agree
- shared deploy package (atomic temp+rename, exec-bit preserving) now backs
  both curator materialization and client deployment
- sync validates and hashes everything before the first mutation; second run
  is a byte-level no-op

internal/gitsource/redact.go

@@ -0,0 +1,16 @@
+package gitsource
+
+import "strings"
+
+// RedactURL strips user:password credentials embedded in a URL so tokens
+// never surface in error messages or logs.
+func RedactURL(u string) string {
+	scheme, rest, found := strings.Cut(u, "://")
+	if !found {
+		return u
+	}
+	if at := strings.Index(rest, "@"); at >= 0 && !strings.Contains(rest[:at], "/") {
+		return scheme + "://" + rest[at+1:]
+	}
+	return u
+}