feat(sproutclaw): modularize webui, extensions, and agent config layout

Restructure local extensions into per-feature directories, split WebUI
into backend modules with slash commands and systemd support, and track
prompts/skills under .pi/agent for portable Gitea deployment.

Co-authored-by: Cursor <cursoragent@cursor.com>

packages/agent/test/harness/skills.test.ts

@@ -113,4 +113,20 @@ Use this skill.
 		expect(skills.map((skill) => skill.name)).toEqual(["skills"]);
 		expect(skills[0]?.content).toBe("Root content");
 	});
+
+	it("ignores README.md at the skills directory root", async () => {
+		const root = createTempDir();
+		const env = new NodeExecutionEnv({ cwd: root });
+		await env.createDir("skills/example", { recursive: true });
+		await env.writeFile("skills/README.md", "# Skills\n\nDirectory documentation.");
+		await env.writeFile(
+			"skills/example/SKILL.md",
+			"---\nname: example\ndescription: Example skill\n---\nUse this skill.",
+		);
+
+		const { skills, diagnostics } = await loadSkills(env, "skills");
+
+		expect(diagnostics).toEqual([]);
+		expect(skills.map((skill) => skill.name)).toEqual(["example"]);
+	});
 });