docs: make CONTRIBUTING and Makefile help match real verification gates (#4667)

CONTRIBUTING.md and the Makefile HEADER advertised nonexistent targets
(make clippy, make check) and claimed 'make pre-commit' runs
format + clippy + check + test, while .config/make/pre-commit.mak
actually runs fmt-check + guard scripts + quick-check with no clippy
and no tests. CONTRIBUTING.md also claimed the repository ships an
automated pre-commit git hook, but no hook is versioned.

- Replace phantom targets with the real ones (clippy-check,
  quick-check, compilation-check)
- Document exactly what pre-commit and pre-pr run, gate by gate,
  with an explicit note that pre-commit runs no clippy and no tests
- Point contributors to 'make pre-pr' as the full pre-PR gate
- Rewrite the git-hooks section to say hooks are optional and not
  versioned; setup-hooks only marks an existing hook executable

No make targets were added or changed; docs/help truth only.

Refs: rustfs/backlog#1153 (infra-9), rustfs/backlog#1155

Makefile

@@ -64,10 +64,11 @@ How to use me:
 
 	🔧 Code Quality:
 		make fmt                                 # Format code
-		make clippy                              # Run clippy checks
-		make test                                # Run tests
-		make pre-commit                          # Run fast pre-commit checks
-		make pre-pr                              # Run full pre-PR checks
+		make clippy-check                        # Run clippy (all targets, all features, -D warnings)
+		make quick-check                         # Fast workspace compile check (excludes e2e_test)
+		make test                                # Script tests + workspace tests + doc tests
+		make pre-commit                          # Fast gate: fmt-check + guard scripts + quick-check (NO clippy, NO tests)
+		make pre-pr                              # Full pre-PR gate: pre-commit gates + clippy-check + test
 
 	🚀 Quick Start:
 		make build                               # Build RustFS binary