refactor(llm-deepseek)!: rename the provider route to deepseek-official

The native adapter's route was named deepseek, colliding with pi-ai's
catalog provider of the same name, so the two DeepSeek paths could never
be mounted side by side. The web settings page needs both configurable at
once. Compositions, fixtures, goldens, scaffolding defaults, and docs all
move together (pre-release, no shim); TUI/session-query-spill/
missing-credential goldens re-recorded through their keyless refresh
modes because provider-name length shifts box padding and spill
truncation points.

examples/tui-agent/tests/tui.snapshot.ts

@@ -36,7 +36,7 @@ import { HeadlessTerminal } from '../../../packages/ui/tui/tests/headless-termin
 const SNAPSHOTS_DIR = join(dirname(fileURLToPath(import.meta.url)), 'snapshots')
 // Keep pre-normalization layout widths identical across macOS and Linux.
 const SNAPSHOT_TMP_ROOT = process.platform === 'win32' ? tmpdir() : '/tmp'
-const PROVIDERS = [{ id: 'deepseek', models: [{ id: 'deepseek-v4-flash', contextWindow: 128_000 }] }]
+const PROVIDERS = [{ id: 'deepseek-official', models: [{ id: 'deepseek-v4-flash', contextWindow: 128_000 }] }]
 const UUID_RE = /[0-9a-f]{8}-[0-9a-f]{4}-[0-9a-f]{4}-[0-9a-f]{4}-[0-9a-f]{12}/gi
 
 type SnapshotMode = 'replay' | 'record' | 'refresh'
@@ -293,7 +293,7 @@ async function runScenario(scenario: Scenario): Promise<ScenarioResult> {
     const handle = await ctx.agents.create({
       sessionId: SessionId('main-session'),
       meta: { cwd },
-      agentOptions: { provider: 'deepseek', model: 'deepseek-v4-flash' },
+      agentOptions: { provider: 'deepseek-official', model: 'deepseek-v4-flash' },
     })
     const agent: Agent = handle.agent
     controller = createTuiChat(ctx, {