Simplify publish workflow: trigger on tag push, drop unused OIDC

crates.io does not support OIDC trusted publishing. Use
CARGO_REGISTRY_TOKEN secret and trigger on v* tag pushes.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

Author: lightsofapollo

.github/workflows/publish.yml

@@ -1,19 +1,15 @@
 name: Publish to crates.io
 
 on:
-  release:
-    types: [published]
+  push:
+    tags: ["v*"]
 
 env:
   CARGO_TERM_COLOR: always
 
 jobs:
   publish:
     runs-on: ubuntu-latest
-    environment: crates-io
-    permissions:
-      id-token: write
-      contents: read
     steps:
       - uses: actions/checkout@v4
       - uses: dtolnay/rust-toolchain@stable