security(deps): bump capnp 0.20 -> 0.25 (RUSTSEC-2025-0143)

Upgrades the capnp runtime and capnpc code-generator in echidna-wire
to clear RUSTSEC-2025-0143 ("Unsound APIs of public constant::Reader
and StructSchema", fixed in >=0.24). capnpc 0.25 regenerates the
wire module identically and the 3 echidna-wire smoke tests pass.

Only remaining cargo-audit warning is RUSTSEC-2025-0134 (rustls-pemfile
unmaintained) pulled transitively via tonic 0.12 in echidna-grpc; that
is tracked as a separate tonic 0.13 bump campaign.

https://claude.ai/code/session_01NaC5RXjTyr5xg9XXUa2FCC

Author: claude

Cargo.lock

@@ -11,7 +11,7 @@ repository  = "https://github.com/hyperpolymath/echidna"
 build       = "build.rs"
 
 [dependencies]
-capnp = "0.20"
+capnp = "0.25"
 
 [build-dependencies]
-capnpc = "0.20"
+capnpc = "0.25"