feat(channel): surface 410 Gone with re-onboard hint instead of HTTP-410 (#2429)

Follow-up to molecule-core#2449 (which taught the platform to return
410 Gone for status='removed'). Without this branch the operator sees
`get_workspace_info failed: HTTP 410 — workspace removed` and has to
guess what to do — exactly the 2026-04-30 silent-fail UX hit on the
hongmingwang tenant.

The new code path:
  1. Detect resp.status === 410 explicitly
  2. Best-effort parse the body for id / removed_at / hint
  3. Throw `Workspace <id> was deleted on the platform at <ts>. <hint>`

The 410-message-formatting is extracted into a pure
`formatRemovedWorkspaceError` helper so it can be unit-tested
without mocking fetch + resolveWatching. Four new bun:test cases:

  - prefers platform-supplied id, removed_at, hint
  - falls back to local workspaceId + default hint when body is empty
  - tolerates null/undefined body (unparseable response)
  - omits ' at <ts>' clause when removed_at is missing

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

server.test.ts

@@ -0,0 +1,49 @@
+// Regression tests for getWorkspaceInfo's 410-handling — pinned via
+// the formatRemovedWorkspaceError pure helper so the test doesn't
+// need to mock fetch + resolveWatching just to read one string.
+//
+// molecule-core#2429 — without these tests, the "your workspace was
+// deleted, re-onboard" message is a 4-line code path that an
+// inattentive refactor could collapse back into the generic
+// "HTTP 410" error we used to surface.
+
+import { describe, expect, it } from 'bun:test'
+import { formatRemovedWorkspaceError } from './server.ts'
+
+describe('formatRemovedWorkspaceError — 410 Gone handling (#2429)', () => {
+  it('prefers the platform-supplied id, removed_at, and hint when present', () => {
+    const msg = formatRemovedWorkspaceError('local-fallback-id', {
+      id: 'real-uuid',
+      removed_at: '2026-04-30T12:00:00Z',
+      hint: 'Custom hint from the platform.',
+    })
+    expect(msg).toBe(
+      'Workspace real-uuid was deleted on the platform at 2026-04-30T12:00:00Z. Custom hint from the platform.',
+    )
+  })
+
+  it('falls back to the local workspaceId + default hint when body is empty', () => {
+    const msg = formatRemovedWorkspaceError('fallback-uuid', {})
+    expect(msg).toBe(
+      'Workspace fallback-uuid was deleted on the platform. Regenerate workspace + token from the canvas → Tokens tab.',
+    )
+  })
+
+  it('tolerates a null/undefined body (unparseable response)', () => {
+    expect(formatRemovedWorkspaceError('uuid', null)).toContain(
+      'Workspace uuid was deleted',
+    )
+    expect(formatRemovedWorkspaceError('uuid', undefined)).toContain(
+      'Regenerate workspace + token',
+    )
+  })
+
+  it('omits the timestamp clause when removed_at is missing', () => {
+    const msg = formatRemovedWorkspaceError('uuid', {
+      id: 'uuid',
+      hint: 'h',
+    })
+    expect(msg).not.toContain(' at ')
+    expect(msg).toBe('Workspace uuid was deleted on the platform. h')
+  })
+})

server.ts

@@ -691,12 +691,39 @@ const GetWorkspaceInfoArgsSchema = z.object({
   ).optional(),
 })
 
+// Pure formatter — kept exportable so server.test.ts can pin the
+// message shape without mocking fetch + resolveWatching just to read
+// one string. molecule-core#2429.
+export function formatRemovedWorkspaceError(
+  workspaceId: string,
+  body: { id?: string; removed_at?: string; hint?: string } | null | undefined,
+): string {
+  const safeBody = body ?? {}
+  const id = safeBody.id ?? workspaceId
+  const hint = safeBody.hint ?? 'Regenerate workspace + token from the canvas → Tokens tab.'
+  const removed = safeBody.removed_at ? ` at ${safeBody.removed_at}` : ''
+  return `Workspace ${id} was deleted on the platform${removed}. ${hint}`
+}
+
 async function getWorkspaceInfo(args: z.infer<typeof GetWorkspaceInfoArgsSchema>): Promise<unknown> {
   const { workspaceId, token } = resolveWatching(args._as_workspace)
   const resp = await fetch(`${PLATFORM_URL}/workspaces/${workspaceId}`, {
     headers: platformHeaders(token),
     signal: AbortSignal.timeout(15_000),
   })
+  if (resp.status === 410) {
+    // molecule-core#2429: platform returns 410 Gone when status='removed'.
+    // Surface a clear "your workspace was deleted, re-onboard" error
+    // instead of a generic HTTP error — without this branch the operator
+    // sees `get_workspace_info failed: HTTP 410` and has to guess why.
+    let body: { id?: string; removed_at?: string; hint?: string } = {}
+    try {
+      body = await resp.json() as typeof body
+    } catch {
+      // best-effort body parse; the error message stands alone
+    }
+    throw new Error(formatRemovedWorkspaceError(workspaceId, body))
+  }
   if (!resp.ok) {
     const errText = await resp.text().catch(() => '')
     throw new Error(`get_workspace_info failed: HTTP ${resp.status} — ${errText.slice(0, 200)}`)