✨ Adopt @spences10/pi-lsp project-local

Declare the read-only LSP extension in .pi/settings.json so it is
shared with the team and auto-installed on project trust.

Pin 0.0.46 explicitly: a bare `pi install` writes `^0.0.10`, and in
semver a caret on 0.0.x pins to exactly 0.0.10, which hard-wires
typescript-language-server and predates TypeScript 7. 0.0.46 detects
the repo's own typescript@7 (no lib/tsserver.js) and spawns
tsc --lsp --stdio against it — no extra server package required.

Commit pi's own .pi/npm/.gitignore sentinel rather than adding a rule
to the project root .gitignore: pi put the file there deliberately, so
leaving it in place (and tracked) is the least-surprise option for a
human reading the tree.

.pi/npm/.gitignore

@@ -0,0 +1,2 @@
+*
+!.gitignore

.pi/settings.json

@@ -0,0 +1,3 @@
+{
+    "packages": ["npm:@spences10/pi-lsp@0.0.46"]
+}