feat(web): a prose mention of a produced file opens it

The chatFileMentions service (provided by ui-deliverables beside its
turn-tail entry, reached via ctx.get) resolves inline-code tokens in the
closing message against the turn's produced locations: exact path or
unique basename links, ambiguity and unknowns stay inert. MarkdownText
gains the optional fileMentions seam — settled renders only, never
inside anchors.

apps/web/tests/produced-file-mentions.e2e.ts

@@ -0,0 +1,162 @@
+// Web e2e scenario: inline-code file mentions in the closing prose. Cold-seeds
+// a built write turn (zero model calls) whose closing message names the written
+// file three ways: by unique basename (links), ambiguously (stays inert), and
+// as a file the turn never touched (stays inert). Package tests cover the
+// resolver in isolation; only the assembled application shows a real write's
+// locations reaching the prose as an opener. The click itself is not driven
+// here: it hands the path to the Host's opener, which would launch a real
+// application on the machine running the suite (the produced-files restraint).
+import type { Browser, Page } from 'playwright'
+import { chromium } from 'playwright'
+import { afterAll, beforeAll, describe, expect, it, onTestFailed } from 'vitest'
+import { CallId, createAssistantMessage, createToolResultMessage, createUserMessage } from '@deepseek-ai/dsh-llm'
+import { SESSION_FORMAT_VERSION, Session, SessionId } from '@deepseek-ai/dsh-session'
+import type {} from '@deepseek-ai/dsh-session-title'
+import {
+  launchWebScaffold, seedSession, watchConsole, webSnapshotMode, type WebScaffold,
+} from './scaffold.ts'
+import { newEnglishPage, saveFailureShot } from './support.ts'
+
+const MODE = webSnapshotMode()
+const SEED_ID = 'produced-file-mentions-web-e2e'
+const DONE = 'FILE_MENTION_DONE'
+
+/** One-part text content for a built message. */
+function text(value: string): { type: 'text'; text: string }[] {
+  return [{ type: 'text', text: value }]
+}
+
+/** The files the built turn writes; `notes.md` is named in prose but never written. */
+const WRITES = ['site/report.html', 'a/style.css', 'b/style.css']
+
+/** Build a settled write turn whose closing prose mentions files in inline code. */
+function mentionFixture(): string {
+  const session = Session.create(SessionId('produced-file-mentions-source'))
+  const eventTimeOrigin = new Date().setHours(12, 0, 0, 0)
+  session.append('turn/start', { turn: 1 })
+  const user = session.append('user/message', createUserMessage({
+    content: [{ type: 'text', text: 'Write the report page and both stylesheets.' }],
+    source: { kind: 'user' },
+  }), { surfaceOp: 'append' })
+  session.append('session/title', {
+    title: 'Produced file mentions',
+    messageSeqs: [user.seq],
+    source: { kind: 'fallback' },
+  })
+  session.append('step/start', { turn: 1, step: 1 })
+  const calls = WRITES.map((path, index) => ({
+    path,
+    callId: CallId(`file-mention-${String(index)}`),
+    args: JSON.stringify({ file_path: path, content: `content of ${path}\n` }),
+  }))
+  session.append('assistant/message', {
+    turn: 1,
+    step: 1,
+    message: createAssistantMessage({
+      content: calls.map(call => ({
+        type: 'tool-call' as const,
+        id: call.callId,
+        name: 'write',
+        arguments: call.args,
+      })),
+      source: { provider: 'deepseek-official', model: 'deepseek-v4-flash' },
+    }),
+  }, { surfaceOp: 'append' })
+  for (const call of calls) {
+    const source = session.append('tool/call', {
+      turn: 1,
+      step: 1,
+      callId: call.callId,
+      name: 'write',
+      arguments: call.args,
+    })
+    session.append('tool/result', {
+      turn: 1,
+      step: 1,
+      message: createToolResultMessage({
+        callId: call.callId,
+        content: text(`Created ${call.path}`),
+        isError: false,
+      }),
+    }, { surfaceOp: 'append', sourceEventSeqs: [source.seq] })
+  }
+  session.append('step/start', { turn: 1, step: 2 })
+  session.append('assistant/message', {
+    turn: 1,
+    step: 2,
+    message: createAssistantMessage({
+      content: [{
+        type: 'text',
+        text: [
+          'Wrote `report.html` plus two `style.css` copies; `notes.md` untouched.',
+          '',
+          DONE,
+        ].join('\n'),
+      }],
+      source: { provider: 'deepseek-official', model: 'deepseek-v4-flash' },
+    }),
+  }, { surfaceOp: 'append' })
+  session.append('step/end', { turn: 1, step: 2 })
+  session.append('turn/end', { turn: 1, reason: { kind: 'completed' } })
+
+  return [
+    JSON.stringify({
+      type: 'session',
+      version: SESSION_FORMAT_VERSION,
+      id: '{{sessionId}}',
+      createdAt: 0,
+      cwd: '{{cwd}}',
+    }),
+    ...session.events.map(event => JSON.stringify({
+      ...event,
+      time: eventTimeOrigin + event.seq * 1_000,
+    })),
+    '',
+  ].join('\n')
+}
+
+describe('web e2e: inline-code mentions of produced files', () => {
+  let scaffold: WebScaffold
+  let browser: Browser
+  let page: Page
+  let tripwire: ReturnType<typeof watchConsole>
+
+  beforeAll(async () => {
+    scaffold = await launchWebScaffold({})
+    await seedSession(scaffold, mentionFixture(), SEED_ID)
+    browser = await chromium.launch()
+    page = await newEnglishPage(browser)
+    tripwire = watchConsole(page)
+    await page.goto(scaffold.baseUrl, { waitUntil: 'load' })
+    await page.waitForSelector('[class*="frame"]', { timeout: 30_000 })
+  }, 120_000)
+
+  afterAll(async () => {
+    await browser?.close()
+    await scaffold?.close()
+  })
+
+  it.skipIf(MODE === 'record')('links the unique mention and leaves ambiguous and unknown code inert', async () => {
+    onTestFailed(() => saveFailureShot(page, 'web-e2e-produced-file-mentions'))
+    const groupRow = page.locator('[role="treeitem"]').first()
+    await groupRow.waitFor({ timeout: 15_000 })
+    await groupRow.click()
+    const sessionRow = page.locator('[role="treeitem"]').nth(1)
+    await sessionRow.waitFor({ timeout: 10_000 })
+    await sessionRow.click()
+    await expect.poll(() => page.getByText(DONE, { exact: true }).count(), { timeout: 15_000 }).toBe(1)
+
+    // Exactly one prose mention links: `report.html` resolves to the written
+    // path; the shared `style.css` basename and unwritten `notes.md` stay code.
+    const mentions = page.locator('[class*="markdown"] code button')
+    await expect.poll(() => mentions.count(), { timeout: 10_000 }).toBe(1)
+    expect(await mentions.first().innerText()).toBe('report.html')
+    expect(await mentions.first().getAttribute('aria-label')).toBe('Open site/report.html')
+    expect(await mentions.first().getAttribute('title')).toBe('site/report.html')
+    // The turn still ends with its produced-files row (all three writes).
+    expect(await page.getByText('Produced', { exact: true }).count()).toBe(1)
+
+    expect(tripwire.pageErrors).toEqual([])
+    expect(tripwire.warnings).toEqual([])
+  }, 90_000)
+})