feat: 接入形态图库与 Seedream 生图操作

展示已有主图、候选图和失败记录，支持单图及批量生成、主图选择。
补充正式 ID 校验、费用确认、图片加载占位和回归测试。
依赖后端 eac8dc3 的项目形态图库只读接口。

src/features/subject-images/useSubjectImages.ts

@@ -0,0 +1,104 @@
+import { computed, ref } from 'vue'
+import { usePolling } from '../../composables/usePolling'
+import { ApiError } from '../../lib/http'
+import { useProjectContext } from '../projects/context'
+import { getOperation, runOperation } from '../workflows/operations'
+import { workflowCheckpoints } from '../workflows/selectors'
+import { subjectImagesApi } from './api'
+import { getImageSession, hasRunningImages } from './model'
+import type { GenerateFormImageInput } from './types'
+
+/** 形态图库统一读取数据库记录并管理单图／批量长请求，不调用生产流程。 */
+export function useSubjectImages() {
+    const context = useProjectContext()
+    const id = computed(() => context.project.value?.id ?? '')
+    const concurrency = ref(2)
+    const force = ref(false)
+    const query = usePolling(id, async (projectId, signal) => {
+        if (!projectId) return []
+        try {
+            const forms = await subjectImagesApi.listForms(projectId, signal)
+            if (
+                forms.some(
+                    form =>
+                        form.subject.projectId !== projectId ||
+                        form.images.some(image => image.subjectFormId !== form.id)
+                )
+            )
+                throw new Error('形态图库返回了不匹配的项目或图片，请刷新后重试。')
+            return forms
+        } catch (error) {
+            if (error instanceof ApiError && error.status === 404)
+                throw new Error(
+                    '后端尚未提供形态图库查询，请更新后端 dev 并重启服务（GET /projects/:id/subject-forms）。',
+                    { cause: error }
+                )
+            throw error
+        }
+    })
+    const forms = computed(() => query.data.value ?? [])
+    const operation = computed(() => getOperation(id.value))
+    const session = computed(() => getImageSession(id.value))
+    const running = computed(() => forms.value.some(form => hasRunningImages(form.images)))
+    const breakdownRunning = computed(
+        () =>
+            workflowCheckpoints(context.checkpoints.value, 'breakdown').at(-1)?.state.workflowExecution?.status ===
+            'running'
+    )
+    const blocked = computed(
+        () =>
+            operation.value.pending ||
+            !!context.error.value ||
+            !!query.error.value ||
+            query.data.value === null ||
+            running.value ||
+            breakdownRunning.value ||
+            context.project.value?.status === 'generating'
+    )
+    const batchValid = computed(() => Number.isSafeInteger(concurrency.value) && concurrency.value > 0)
+
+    /** 捕获正式 Form ID，生成后重新读取图片；刷新失败也不自动重发有费用的请求。 */
+    async function generate(formId: string, input: GenerateFormImageInput) {
+        if (blocked.value) return
+        const form = forms.value.find(item => item.id === formId)
+        if (!form) return
+        const projectId = id.value
+        await runOperation(projectId, `生成 ${form.subject.name} · ${form.name} 图片`, async () => {
+            const image = await subjectImagesApi.generate(formId, input)
+            if (!image || image.subjectFormId !== formId || image.status !== 'completed' || !image.imageUrl)
+                throw new Error(image?.error || '接口未返回已完成的图片，请先刷新图片记录核对后端状态。')
+        })
+        await query.refresh()
+    }
+
+    /** 批量始终面向整个项目，不受页面筛选影响；force 仅新增候选图，不替换已有主图。 */
+    async function generateProject() {
+        if (blocked.value || !batchValid.value || !forms.value.length) return
+        const projectId = id.value
+        const input = { provider: 'seedream' as const, concurrency: concurrency.value, force: force.value }
+        const target = getImageSession(projectId)
+        target.receipt = null
+        await runOperation(projectId, '批量生成项目形态图片', async () => {
+            target.receipt = {
+                title: input.force ? '为全项目新增候选图' : '补齐项目主参考图',
+                result: await subjectImagesApi.generateProject(projectId, input)
+            }
+        })
+        await query.refresh()
+    }
+
+    return {
+        id,
+        forms,
+        query,
+        operation,
+        session,
+        concurrency,
+        force,
+        blocked,
+        running,
+        batchValid,
+        generate,
+        generateProject
+    }
+}