chore: DX improvements — typos, blame-ignore, PR template, registry checklist (#120)

* chore: add workspace clippy lints, release profiles, COMPAT.md, diff-registry.sh

- Workspace clippy lints: or_fun_call, redundant_clone, collection_is_never_read,
  naive_bytecount, stable_sort_primitive, large_types_passed_by_value, assigning_clones
- Fix or_fun_call in cargo_registry.rs (unwrap_or -> unwrap_or_else)
- Release profiles: release (thin LTO) + release-official (full LTO, codegen-units=1)
- COMPAT.md: protocol compatibility matrix for all 7 registries (40 endpoints)
- scripts/diff-registry.sh: differential smoke tests (Docker/npm/Cargo/PyPI/Go/Raw)

* ci: add typos spell-check job and config

* chore: add .git-blame-ignore-revs for bulk fmt/clippy commits

* chore: unify PR template with What/Why/Checklist format

* docs: add new registry checklist and improve contributing guide

* fix: correct typos action SHA to v1.45.0

_typos.toml

@@ -0,0 +1,10 @@
+[default.extend-words]
+# HashiCorp is not a typo
+Hashi = "Hashi"
+# flate2 is a Rust crate for compression
+flate = "flate"
+# grep pattern fragment in lint script
+validat = "validat"
+
+[files]
+extend-exclude = ["vendor/", "*.lock", "target/", "fuzz/corpus/"]