chore(spawner): bump version to 1.20.4 for crates.io republish

The 1.20.3 version on crates.io lacks the with_stderr_log method
that downstream crates (terraphim-agents) depend on. Bump to 1.20.4
so the publish workflow can upload the correct code.

Refs #2260

Author: Alex

crates/terraphim_spawner/Cargo.toml

@@ -1,6 +1,6 @@
 [package]
 name = "terraphim_spawner"
-version = "1.20.2"
+version = "1.20.4"
 edition = "2021"
 authors = ["Terraphim Team <team@terraphim.ai>"]
 description = "Agent spawner for Terraphim with health checking and output capture"