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/pi-ext/mcpctl-pi.ts

@@ -177,6 +177,30 @@ function convertProp(raw: unknown): TSchema {
   }
 }
 
+/**
+ * Order and filter the project list for the picker.
+ *
+ * Ordering: the active project first (most likely pick), then alphabetical.
+ * Filtering: space-separated terms, ALL of which must appear as
+ * case-insensitive substrings — so `home auto` finds `homeautomation`. A blank
+ * query keeps everything.
+ *
+ * Exported so the behaviour is unit-tested rather than eyeballed through a TUI.
+ */
+export function filterProjects(projects: string[], query: string, active: string | null): string[] {
+  const ordered = [...projects].sort((a, b) => {
+    if (a === active) return -1;
+    if (b === active) return 1;
+    return a.localeCompare(b);
+  });
+  const terms = query.toLowerCase().split(/\s+/).filter((t) => t.length > 0);
+  if (terms.length === 0) return ordered;
+  return ordered.filter((p) => {
+    const name = p.toLowerCase();
+    return terms.every((t) => name.includes(t));
+  });
+}
+
 /** Sanitize a name for use as a pi tool name segment ([a-z0-9_]). */
 function safeSegment(name: string): string {
   return name.toLowerCase().replace(/[^a-z0-9_]+/g, "_").replace(/^_+|_+$/g, "") || "x";
@@ -402,6 +426,47 @@ export default function (pi: ExtensionAPI) {
     },
   });
 
+  /** Above this many projects, arrowing through the list stops being usable. */
+  const FILTER_THRESHOLD = 20;
+  /** Never render more than this in one selector, even after filtering. */
+  const MAX_SHOWN = 50;
+
+  /**
+   * Choose a project, asking for a filter first when the list is long.
+   *
+   * pi's selector is a plain arrow-key list — `ExtensionUIDialogOptions` has no
+   * search and `ExtensionSelectorComponent` ignores typed characters — so the
+   * filtering has to happen before the list is handed over. Real installs run
+   * to hundreds of projects (smoke-test leftovers included), where scrolling is
+   * hopeless.
+   *
+   * Terms are space-separated and ALL must match, case-insensitively, as
+   * substrings: `home auto` finds `homeautomation`. Blank shows everything.
+   */
+  async function pickProject(ctx: ExtensionContext, projects: string[]): Promise<string | undefined> {
+    let candidates = filterProjects(projects, "", activeProject);
+    if (candidates.length > FILTER_THRESHOLD) {
+      const query = await ctx.ui.input(
+        `Filter ${String(candidates.length)} projects (blank = all, Esc = cancel)`,
+        "e.g. home auto",
+      );
+      if (query === undefined) return undefined; // cancelled
+      candidates = filterProjects(projects, query, activeProject);
+      if (candidates.length === 0) {
+        ctx.ui.notify(`No project matches '${query}'`, "warning");
+        return undefined;
+      }
+    }
+
+    const truncated = candidates.length > MAX_SHOWN;
+    const shown = truncated ? candidates.slice(0, MAX_SHOWN) : candidates;
+    const title = truncated
+      // Say what was dropped: a silently capped list reads as "that's all of them".
+      ? `Switch to project (${String(MAX_SHOWN)} of ${String(candidates.length)} matches — narrow the filter)`
+      : `Switch to project (${String(shown.length)})`;
+    return ctx.ui.select(title, shown);
+  }
+
   async function switchProject(ctx: ExtensionContext): Promise<void> {
     let projects: string[] = [];
     try {
@@ -414,7 +479,7 @@ export default function (pi: ExtensionAPI) {
       ctx.ui.notify("No projects returned by mcpd", "warning");
       return;
     }
-    const picked = await ctx.ui.select("Switch to project", projects);
+    const picked = await pickProject(ctx, projects);
     if (!picked) return;
 
     // Tear down old project's session + active tools.