chore(deps): bump @ai-sdk/openai to 3.0.73 and ai to 6.0.208 in /agent-service [release/v1.2 backport] (#5872)

### What changes were proposed in this PR?

Backport of #5816 to `release/v1.2`: bump @ai-sdk/openai to
3.0.73 and ai to 6.0.208 in /agent-service.

Cherry-pick with one conflict resolved: kept elysia at release/v1.2
value 1.4.27 (this PR must not bump it) while taking the ai-SDK
transitive eventsource-parser 3.0.6→3.1.0. package.json/bun.lock applied
cleanly.

**Risk:** 🔴 **MAJOR** — ai 5→6 and openai-provider 2→3. Runtime AI SDK;
highest behavioral risk of the set.

### Any related issues, documentation, discussions?

Backports #5816 (merged to `main`). No `release/*` label is
added — this PR *is* the backport, and a release label would trigger a
backport-of-a-backport precheck. CI stacks auto-select from the
file-based labels.

### How was this PR tested?

Mirrors the change already merged and CI-validated on `main`
(#5816); verified the backport diff equals the original
bump and applies onto `release/v1.2`. Manual verification:

Booted agent-service and ran an end-to-end LLM call through the agent
(chat + tool-use + streaming) to confirm the new SDK shapes work at
runtime.

### Was this PR authored or co-authored using generative AI tooling?

Generated-by: Claude Code (Opus 4.8 [1M context])

Signed-off-by: dependabot[bot] <support@github.com>
Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>

Author: aglinxinyuan

agent-service/LICENSE-binary

@@ -211,13 +211,13 @@ Dependencies under the Apache License, Version 2.0
 --------------------------------------------------------------------------------
 
 Agent service npm packages:
-  - @ai-sdk/gateway@2.0.18
-  - @ai-sdk/openai@2.0.79
-  - @ai-sdk/provider-utils@3.0.18
-  - @ai-sdk/provider@2.0.0
+  - @ai-sdk/gateway@3.0.133
+  - @ai-sdk/openai@3.0.73
+  - @ai-sdk/provider-utils@4.0.30
+  - @ai-sdk/provider@3.0.10
   - @opentelemetry/api@1.9.0
-  - @vercel/oidc@3.0.5
-  - ai@5.0.108
+  - @vercel/oidc@3.2.0
+  - ai@6.0.208
   - rxjs@7.8.2
   - typescript@6.0.3
 
@@ -230,7 +230,7 @@ Agent service npm packages:
   - @elysiajs/cors@1.4.0
   - @pinojs/redact@0.4.0
   - @sinclair/typebox@0.34.41
-  - @standard-schema/spec@1.0.0
+  - @standard-schema/spec@1.1.0
   - @tokenizer/inflate@0.4.1
   - @tokenizer/token@0.3.0
   - @types/bun@1.3.14
@@ -242,7 +242,7 @@ Agent service npm packages:
   - dagre@0.8.5
   - debug@4.4.3
   - elysia@1.4.29
-  - eventsource-parser@3.0.6
+  - eventsource-parser@3.1.0
   - exact-mirror@0.2.7
   - fast-decode-uri-component@1.0.1
   - fast-deep-equal@3.1.3

agent-service/bun.lock

@@ -15,9 +15,9 @@
     "format:check": "prettier --check \"src/**/*.{ts,tsx,json}\""
   },
   "dependencies": {
-    "@ai-sdk/openai": "2.0.79",
+    "@ai-sdk/openai": "3.0.73",
     "@elysiajs/cors": "1.4.0",
-    "ai": "5.0.108",
+    "ai": "6.0.208",
     "ajv": "8.18.0",
     "dagre": "0.8.5",
     "elysia": "1.4.29",