ci: gate frontend and rust checks by changed paths (#8433)

The paths-filter output in lint-clippy.yml only gated two echo steps;
checkout, toolchain setup and clippy itself ran unconditionally, so
frontend-only PRs still burned a 3-runner matrix on a full clippy build
plus the logging-check tool install.

- lint-clippy/rustfmt/frontend-check: move path filters to workflow
  level so irrelevant PRs spawn no runner at all
- split contract-parity into its own workflow; its trigger set spans
  both sides and workflow paths cannot vary per job
- clippy paths now cover crates/** and workspace Cargo files, which the
  old src-tauri/** filter missed

dev has no required status checks, so path-filtered workflows cannot
get stuck in "Expected".

scripts/contract-inputs.json

@@ -17,7 +17,7 @@
     "pnpm-lock.yaml",
     "pnpm-workspace.yaml",
     "scripts/contract-inputs.json",
-    ".github/workflows/frontend-check.yml",
+    ".github/workflows/contract-parity.yml",
     ".husky/pre-push"
   ]
 }