feat(admin): web-based skill management with file editor

Add full skill lifecycle to the org-admin web surface: create, read,
edit, disable. Skills are directories (SKILL.md manifest + supporting
files), content-addressed by SHA-256 in an immutable store.

Backend:
- skillStore: extract commitSkillContent (shared populate→inspect→
  dedup→atomic rename); add importSkillFromFiles (in-memory file list
  ingestion) and readSkillFiles (read stored version back as UTF-8)
- configuration: add installSkillFromFiles, readSkillFiles, disableSkill
  (soft-delete + archive bound role sessions), updateSkillDescription
  (label-only, no archival); refactor installSkill to share
  commitInstalledSkill
- agentConfigRoutes: wire skillStoreRoot; add GET
  /agent-skills/:name/files, PUT /agent-skills/:name (create/replace),
  PATCH /agent-skills/:name (description/disable)
- orgRoutes: pass readSkillStoreRoot() to agent config routes

Frontend:
- api.ts: agentSkillFiles, installAgentSkill, patchAgentSkill methods
- SkillEditor.svelte: file tree + text editor + version/description form
- skills/+page.svelte: skill list, create form (generates SKILL.md
  template), per-skill editor
- layout: add 技能 nav item

ADR-0018: update Decision to reflect web surface joining host-console
CLI in the shared content-addressed ingestion pipeline.

Spec (AgentRole.lean): unchanged — storage mechanism is OPEN, web
installation is one implementation of it.

hub/admin-web/src/routes/+layout.svelte

@@ -25,6 +25,7 @@
 		{ key: 'projects', label: '项目', icon: 'projects' as const },
 		{ key: 'capacity', label: '容量', icon: 'overview' as const },
 		{ key: 'provider', label: '供应方', icon: 'provider' as const },
+		{ key: 'skills', label: '技能', icon: 'roles' as const },
 		{ key: 'roles', label: '角色', icon: 'roles' as const },
 		{ key: 'feishu', label: '飞书', icon: 'feishu' as const },
 	];

hub/admin-web/src/routes/admin/org/[slug]/skills/+page.svelte

@@ -0,0 +1,141 @@
+<script lang="ts">
+	import { page } from '$app/state';
+	import { api, type AgentSkillRow, type SkillFileEntry } from '$lib/api';
+	import PageHeader from '$lib/components/PageHeader.svelte';
+	import LoadingState from '$lib/components/LoadingState.svelte';
+	import ErrorBanner from '$lib/components/ErrorBanner.svelte';
+	import EmptyState from '$lib/components/EmptyState.svelte';
+	import SkillEditor from '$lib/components/SkillEditor.svelte';
+	import { toastError, toastSuccess } from '$lib/toast';
+
+	const slug = $derived(page.params.slug ?? '');
+
+	let skills = $state<AgentSkillRow[]>([]);
+	let loading = $state(true);
+	let error = $state<string | null>(null);
+
+	let showNewSkill = $state(false);
+	let newSkillName = $state('');
+	let newSkillVersion = $state('0.1.0');
+	let newSkillDescription = $state('');
+	let creating = $state(false);
+
+	async function load() {
+		loading = true;
+		error = null;
+		try {
+			const res = await api.agentSkills(slug);
+			skills = res.skills;
+		} catch (err) {
+			error = err instanceof Error ? err.message : String(err);
+		} finally {
+			loading = false;
+		}
+	}
+
+	async function createSkill() {
+		const name = newSkillName.trim();
+		if (name === '') {
+			toastError('技能名称不能为空');
+			return;
+		}
+		if (!/^[a-z0-9][a-z0-9-]{0,63}$/.test(name)) {
+			toastError('技能名称仅允许小写字母、数字和连字符，且以字母或数字开头');
+			return;
+		}
+		const version = newSkillVersion.trim();
+		if (version === '') {
+			toastError('版本号不能为空');
+			return;
+		}
+		creating = true;
+		try {
+			const manifest = buildManifest(name, newSkillDescription.trim());
+			const files: SkillFileEntry[] = [{ path: 'SKILL.md', content: manifest }];
+			const result = await api.installAgentSkill(slug, name, { version, files });
+			toastSuccess(`技能 ${result.name} 已创建`);
+			newSkillName = '';
+			newSkillDescription = '';
+			showNewSkill = false;
+			await load();
+		} catch (err) {
+			toastError(err instanceof Error ? err.message : String(err));
+		} finally {
+			creating = false;
+		}
+	}
+
+	function buildManifest(name: string, description: string): string {
+		const desc = description === '' ? name : description;
+		return `---\nname: ${name}\ndescription: ${desc}\n---\n# ${name}\n\n`;
+	}
+
+	function onInstalled(_result: { id: string; name: string; contentDigest: string }) {
+		load();
+	}
+
+	function onDisabled(_name: string) {
+		load();
+	}
+
+	$effect(() => {
+		if (slug) load();
+	});
+</script>
+
+<PageHeader
+	title="技能"
+	description="技能是组织级 Agent 能力包：一个包含 SKILL.md manifest 的目录。技能内容按 SHA-256 content-addressed 存储，变更后绑定角色的活跃会话自动归档。"
+/>
+
+{#if loading}
+	<LoadingState />
+{:else if error}
+	<ErrorBanner message={error} onretry={load} />
+{:else}
+	<div class="saas-card-pad mb-6">
+		<div class="flex items-center justify-between">
+			<h2 class="saas-section-title">新建技能</h2>
+			<button class="text-sm text-primary-700 hover:text-primary-900" onclick={() => (showNewSkill = !showNewSkill)}>
+				{showNewSkill ? '取消' : '+ 新建'}
+			</button>
+		</div>
+		{#if showNewSkill}
+			<div class="mt-4 grid gap-3 sm:grid-cols-[12rem_8rem_1fr_auto]">
+				<input
+					class="saas-input font-mono text-sm"
+					placeholder="技能名（如 typst-help）"
+					bind:value={newSkillName}
+				/>
+				<input
+					class="saas-input text-sm"
+					placeholder="版本号"
+					bind:value={newSkillVersion}
+				/>
+				<input
+					class="saas-input text-sm"
+					placeholder="描述"
+					bind:value={newSkillDescription}
+				/>
+				<button class="saas-btn-primary" onclick={createSkill} disabled={creating}>
+					{creating ? '创建中…' : '创建'}
+				</button>
+			</div>
+			<p class="mt-2 text-xs text-surface-600">
+				技能名称仅允许小写字母、数字和连字符，且以字母或数字开头。创建后会生成 SKILL.md 模板。
+			</p>
+		{/if}
+	</div>
+
+	{#if skills.length === 0}
+		<div class="saas-card">
+			<EmptyState title="暂无技能" description="新建一个技能，然后在角色管理中绑定到角色。" />
+		</div>
+	{:else}
+		<div class="space-y-4">
+			{#each skills as skill (skill.id)}
+				<SkillEditor {slug} {skill} oninstalled={onInstalled} ondisabled={onDisabled} />
+			{/each}
+		</div>
+	{/if}
+{/if}