counters: wire redb search hits into daemon RPC

memory-search now records which nodes it finds via the daemon's
record-hits RPC endpoint. The daemon owns the redb database
exclusively, avoiding file locking between processes.

The rename agent reads hit counts to deprioritize nodes that are
actively being found by search — renaming them would break working
queries. Daily check decays counters by 10% so stale hits fade.

Also switched RPC command reading from fixed 256-byte buffer to
read_to_string for unbounded command sizes.

Cargo.lock

@@ -1890,6 +1890,7 @@ dependencies = [
  "peg",
  "ratatui",
  "rayon",
+ "redb",
  "regex",
  "rkyv",
  "serde",
@@ -2229,6 +2230,15 @@ version = "0.5.5"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "03251193000f4bd3b042892be858ee50e8b3719f2b08e5833ac4353724632430"
 
+[[package]]
+name = "redb"
+version = "2.6.3"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "8eca1e9d98d5a7e9002d0013e18d5a9b000aee942eb134883a82f06ebffb6c01"
+dependencies = [
+ "libc",
+]
+
 [[package]]
 name = "redox_syscall"
 version = "0.5.18"