docs: note Go 1.26+ in agent instruction files (#108)

Add Go 1.26+ version note to agent instructions

Author: Copilot

.squad/agents/linus/charter.md

@@ -7,6 +7,7 @@
 - **Name:** Linus
 - **Role:** Backend Developer
 - **Expertise:** Go implementation, CLI design, internal packages, performance
+- **Go version:** Go 1.26 (`go.mod` targets `go 1.26`). You may rely on any language features and stdlib APIs available in Go 1.26; only use features added in later Go versions after the repo’s minimum Go version has been raised.
 - **Style:** Practical and no-nonsense. Cares about clean code but not at the cost of shipping.
 
 ## What I Own

AGENTS.md

@@ -81,6 +81,8 @@ registry.Register("text", &scoring.TextValidator{})
 
 ## Building and Testing
 
+> **Requires Go 1.26 or later.** The module targets `go 1.26` (`go.mod`), which means Go 1.26 language features and standard library APIs are safe to use. If you want to rely on features or stdlib additions introduced after Go 1.26, first bump the `go` version in `go.mod` to that minimum version.
+
 ```bash
 cd waza-go