🔧 Clean dist before each build

tsc does not prune orphaned emit output, so dropping declarationMap left
stale *.d.ts.map files in dist/ until a manual clean. A prebuild hook now
empties dist/ first, keeping the build reproducible. It deliberately leaves
coverage/ alone, since the manual `clean` resets both.

README.md

@@ -39,6 +39,7 @@ Each tool's configuration trade-off is recorded in [Tooling decisions](#tooling-
 The choice and configuration of each tool above is the result of deliberate trade-offs, not defaults. The non-obvious ones:
 
 - **`tsconfig.json` extends `@tsconfig/strictest` + `@tsconfig/node26`**; `tsconfig.build.json` extends it to add the emit-only options (`declaration`, `sourceMap`, `inlineSources`, `outDir`, `target: es2024`, `rewriteRelativeImportExtensions: true`) and to exclude test files. `inlineSources` embeds the original TypeScript in `dist/*.js.map`, so debuggers can map into `src/` without it being shipped; `declarationMap` is intentionally off because a `.d.ts.map` cannot embed source and would dangle. This separation lets the editor and CI type-check from one config while the build emits from the other.
+- **`npm run build` first runs a `prebuild` hook that empties `dist/`.** `tsc` does not prune orphaned emit output — dropping `declarationMap`, for example, left stale `*.d.ts.map` files behind — so the build must start from an empty `dist/` to be reproducible. `prebuild` removes only `dist`; the manual `clean` still resets `dist` + `coverage`, so a local coverage report survives a build.
 - **Source imports use `.ts` extensions** so `node --strip-types` resolves them at test time. `rewriteRelativeImportExtensions: true` in `tsconfig.build.json` rewrites them to `.js` in the emitted JavaScript; the emitted `.d.ts` keep the `.ts` specifier, which TypeScript >= 5.0 resolves (see [Requirements](#requirements)), so no post-processing step is needed.
 - **Type-aware oxlint is enabled declaratively** via `options.typeAware: true` in `.oxlintrc.json` (powered by `oxlint-tsgolint`). The script commands stay clean — no CLI flag — and type-aware mode is a property of the config, not the invocation.
 - **Source-level `oxlint-disable` directives** are used for known type-aware false positives (see `src/pattern.ts`, `src/match.ts`, `src/index.test.ts`). The disable lives next to the code it silences, not in `.oxlintrc.json`, so the trade-off is visible to anyone reading the source.

cspell.json

@@ -28,6 +28,7 @@
         "runwisp",
         "glab",
         "postversion",
+        "prebuild",
         "Zilla",
         "kacl",
         "bestikk",

package.json

@@ -38,6 +38,7 @@
     },
     "scripts": {
         "build": "tsc -p tsconfig.build.json",
+        "prebuild": "rm -rf dist",
         "check": "npm run check:tsc && npm run check:oxlint && npm run check:oxfmt && npm run check:cspell",
         "check:cspell": "cspell lint ${LEFTHOOK_FILES:-.}",
         "check:oxfmt": "oxfmt --check ${LEFTHOOK_FILES:-.}",