feat(pi): filter the project picker instead of scrolling hundreds of rows

pi's selector is a plain arrow-key list: `ExtensionUIDialogOptions` has no
search field and `ExtensionSelectorComponent` ignores typed characters, so
filtering has to happen before the list is handed over. With 356 projects —
most of them `smoke-proj-none-*` leftovers — arrowing to the one you want is
hopeless.

Above 20 projects the picker now asks for a filter first. Terms are
space-separated and all must match as case-insensitive substrings, so
`home auto` finds `homeautomation`. Blank shows everything, Esc cancels.

The active project sorts first (most likely pick), then alphabetical. A
result set over 50 is capped, and the title says what was dropped — a
silently truncated list reads as "that's all of them".

The ordering and matching are extracted into an exported `filterProjects` so
they are unit-tested rather than eyeballed through a TUI.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_017BMXdb2qZbPSh8Q7XpTyjB

src/cli/tests/config/pi-project-filter.test.ts

@@ -0,0 +1,73 @@
+import { describe, it, expect } from 'vitest';
+import { filterProjects } from '../../../pi-ext/mcpctl-pi.js';
+
+/**
+ * pi's selector is a plain arrow-key list — no search — so the project picker
+ * filters before handing the list over. Real installs run to hundreds of
+ * projects, where scrolling is hopeless.
+ */
+const PROJECTS = [
+  'smoke-proj-none-mohimh46',
+  'homeautomation',
+  'docmost',
+  'copy-homeautomation',
+  'labctl',
+  'mcpctl-development',
+  'sre',
+];
+
+describe('filterProjects', () => {
+  it('puts the active project first, then sorts alphabetically', () => {
+    expect(filterProjects(PROJECTS, '', 'labctl')).toEqual([
+      'labctl',
+      'copy-homeautomation',
+      'docmost',
+      'homeautomation',
+      'mcpctl-development',
+      'smoke-proj-none-mohimh46',
+      'sre',
+    ]);
+  });
+
+  it('sorts alphabetically when nothing is active', () => {
+    expect(filterProjects(PROJECTS, '', null)[0]).toBe('copy-homeautomation');
+  });
+
+  it('keeps everything for a blank or whitespace query', () => {
+    expect(filterProjects(PROJECTS, '', null)).toHaveLength(PROJECTS.length);
+    expect(filterProjects(PROJECTS, '   ', null)).toHaveLength(PROJECTS.length);
+  });
+
+  it('matches case-insensitive substrings', () => {
+    expect(filterProjects(PROJECTS, 'HOMEAUTO', null)).toEqual([
+      'copy-homeautomation',
+      'homeautomation',
+    ]);
+  });
+
+  it('requires every space-separated term to match', () => {
+    // "home auto" finds homeautomation even though the terms aren't adjacent...
+    expect(filterProjects(PROJECTS, 'home auto', null)).toEqual([
+      'copy-homeautomation',
+      'homeautomation',
+    ]);
+    // ...and a term that matches nothing eliminates the row.
+    expect(filterProjects(PROJECTS, 'home zzz', null)).toEqual([]);
+  });
+
+  it('narrows the smoke-test noise that motivated this', () => {
+    const many = [...PROJECTS, ...Array.from({ length: 300 }, (_, i) => `smoke-proj-none-x${String(i)}`)];
+    expect(filterProjects(many, 'smoke', null)).toHaveLength(301);
+    expect(filterProjects(many, 'ctl', null)).toEqual(['labctl', 'mcpctl-development']);
+  });
+
+  it('leaves the caller with an empty list rather than a bad match', () => {
+    expect(filterProjects(PROJECTS, 'nosuchproject', null)).toEqual([]);
+  });
+
+  it('does not mutate the input', () => {
+    const input = [...PROJECTS];
+    filterProjects(input, 'home', 'sre');
+    expect(input).toEqual(PROJECTS);
+  });
+});