📝 Document the .pi extension install model

.pi/settings.json is the shared, committed declaration and .pi/npm/ is
a gitignored cache pi recreates on a trusted startup, so the generated
.gitignore is intentional and nothing needs tracking. Record this in
the README tooling notes and close the reproducibility item as
resolved by design.

README.md

@@ -47,7 +47,7 @@ The choice and configuration of each tool above is the result of deliberate trad
 - **`check:tsc` runs first** in the `npm run check` chain so a type error short-circuits the rest (faster feedback than letting oxlint/oxfmt run and then failing on tsc at the end).
 - **The pre-commit hook sets the `LEFTHOOK_FILES` env var** to the staged-files list, and the affected scripts use `${LEFTHOOK_FILES:-<default>}` to default to the whole project when invoked manually. This keeps `package.json#scripts` as the single source of truth for the underlying commands — `lefthook.yml` only describes _what to run on which files_.
 - **`tslib` and `type-fest` are deliberately not used.** `tslib` is a runtime helper for old ES3/ES5 targets (the project targets ES2024); `type-fest` was never imported. knip caught both.
-- **`@spences10/pi-lsp` is pinned to `0.0.46` and is read-only by design.** The package inspects `node_modules/typescript`, sees major ≥ 7 with no `lib/tsserver.js` (true of the `typescript-go` / `tsgo` port), and spawns the repo's own `tsc --lsp --stdio` binary — no `typescript-language-server` dependency is required. Earlier releases (`≤ 0.0.10`) hard-wire to `typescript-language-server --stdio` and are TS6-only. The tool is _intermediate_ agent feedback (hover, references, definition, symbols, diagnostics); it has no rename / code-action / apply-edit surface, and never a correctness gate — `npm run check` / `verify` remain that.
+- **`@spences10/pi-lsp` is pinned to `0.0.46` and is read-only by design.** The package inspects `node_modules/typescript`, sees major ≥ 7 with no `lib/tsserver.js` (true of the `typescript-go` / `tsgo` port), and spawns the repo's own `tsc --lsp --stdio` binary — no `typescript-language-server` dependency is required. Earlier releases (`≤ 0.0.10`) hard-wire to `typescript-language-server --stdio` and are TS6-only. The tool is _intermediate_ agent feedback (hover, references, definition, symbols, diagnostics); it has no rename / code-action / apply-edit surface, and never a correctness gate — `npm run check` / `verify` remain that. `.pi/settings.json` is the shared, committed declaration; `.pi/npm/` is a gitignored install cache that pi recreates automatically on a trusted startup (it runs `npm install` for any missing project package), so the cache is deliberately not tracked.
 
 ### Requirements