feat(typos): add typos spell-check module

[kyle-sexton]

Adds a referenceable typos spell-check module, a vertical slice mirroring the markdown/powershell/editorconfig modules.

Contents

• modules/typos/_typos.toml — decoupled base config: universal ignores only (inline spellchecker: disable directives, braced GUID/UUID literals, *.min.* exclude). Ships no domain words; adopters extend.
• modules/typos/typos.test.sh — shell-harness test (good → exit 0, bad → exit 2, asserts a correction is reported).
• modules/typos/README.md — engine, the blessed inline-directive convention, adopt-in-a-repo guidance.
• fixtures/typos/{good,bad} — clean prose (incl. a working disable-line directive) vs. real misspellings.
• .github/workflows/typos.yml — SHA-pinned CI: install binary via taiki-e/install-action, self-lint the tree, run fixtures.

CI design note

The crate-ci/typos action runs over the full tree and exposes no --exclude input, so the intentionally-misspelled bad fixtures would fail a self-lint. CI instead installs the binary and runs typos --config … --exclude 'fixtures/*/bad/' . directly — keeping the published config adopter-clean, consistent with the editorconfig/markdown invocation-level exclusion decision.

Validation (local, all green)

good fixture exit 0 · bad fixture exit 2 · self-dogfood exit 0 · full shell harness 5/5 · shellcheck -x + actionlint clean · markdown + editorconfig self-lint clean.