fix: bump CI Rust to 1.87 for let-chains, replace retired macos-13

let_chains was stabilized in Rust 1.87, not 1.85 (which only added
edition 2024). Also replaces retired macos-13 runner with macos-15-intel.

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

Author: thrashr888

.github/workflows/ci.yml

@@ -8,8 +8,8 @@ on:
 
 env:
   CARGO_TERM_COLOR: always
-  # Rust 1.85+ required for edition 2024
-  RUST_VERSION: "1.85"
+  # Rust 1.87+ required for let-chains (edition 2024)
+  RUST_VERSION: "1.87"
 
 jobs:
   check:
@@ -98,7 +98,7 @@ jobs:
           - os: macos-latest
             target: aarch64-apple-darwin
             artifact: agentkernel-darwin-arm64
-          - os: macos-13
+          - os: macos-15-intel
             target: x86_64-apple-darwin
             artifact: agentkernel-darwin-x64
     steps:

.github/workflows/release.yml

@@ -7,8 +7,8 @@ on:
 
 env:
   CARGO_TERM_COLOR: always
-  # Rust 1.85+ required for edition 2024
-  RUST_VERSION: "1.85"
+  # Rust 1.87+ required for let-chains (edition 2024)
+  RUST_VERSION: "1.87"
 
 permissions:
   contents: write
@@ -29,7 +29,7 @@ jobs:
           - os: macos-latest
             target: aarch64-apple-darwin
             artifact: agentkernel-darwin-arm64
-          - os: macos-13
+          - os: macos-15-intel
             target: x86_64-apple-darwin
             artifact: agentkernel-darwin-x64
     steps: