chore: update ai-sdk family and node pin

[ThomasK33]

Routine anti-rot batch update: AI SDK family (minor/patch only) plus the Node toolchain pin.

Dependency bumps

Package	Old	New	Where
ai	^7.0.79	^7.0.83	agent (dev), provider (dev), release-please-ai (dep)
@ai-sdk/anthropic	^4.0.42	^4.0.44	provider (dep), release-please-ai (dep)
@ai-sdk/openai-compatible	^3.0.37	^3.0.39	provider (dep)
@ai-sdk/provider-utils	^5.0.30	^5.0.32	sandbox (dev)
@ai-sdk/react	4.0.82	4.0.86	agent (dev, exact pin preserved)
@ai-sdk/harness	^1.0.87	^1.0.91	sandbox (dev)
@ai-sdk/harness-claude-code	^1.0.90	^1.0.94	sandbox (dev)
@ai-sdk/tui	^1.0.80	^1.0.84	sandbox (dev)
node (mise pin)	26.7.0	26.8.1	mise.toml, mise.lock, ci.yml matrix + comments

Published peerDependency ranges are untouched (ai ^7.0.0 in agent/provider; @ai-sdk/harness ^1.0.0 and @ai-sdk/provider-utils ^5.0.0 in sandbox). typescript intentionally not touched (7.x deferred per #99).

Incidental: pnpm install auto-appended transitive @ai-sdk/mcp@2.0.39 to minimumReleaseAgeExclude in pnpm-workspace.yaml (same pattern as existing entries).

Upstream changelog review

Patch-only across the range; no dev-API/breaking changes affecting our usage (sandbox imports only HarnessV1SandboxProvider / HarnessV1NetworkSandboxSession / HarnessV1PortEndpoint types plus HarnessAgent/createClaudeCode in examples — all unchanged). No code adaptations needed. Notable upstream items:

• @ai-sdk/harness 1.0.90: hardened credential brokering (applies only with correct ephemeral secret) — internal to the harness bridge.
• ai 7.0.80–7.0.83: persisted tool-call schema validation, tool-approval denial continuation, mid-stream provider error normalization, stitchable-stream cancellation fix.

Adaptation: node 26.8 test scheduling fix

The Node 26.8.1 CI cell deterministically failed one agent unit test (does not retain the stream when an abort lands while the pause's tool calls are being yielded) that passed on 22/24. Root cause (minimal repro in plain node, bisected across 22 / 26.7.0 / 26.8.1): Node 26.8's whatwg-stream pull path lost a microtask hop (nodejs/node#65138, "cut promise churn in webstreams hot paths"), so the ReadableStream HWM=1 refill pull now resumes the turn generator past its abort checkpoints before a consumer continuation two hops away runs — the test's abort() then landed after the segment had already settled as a healthy retained pause (a documented, designed state: "aborted between segments"), not mid-yield as the test intends. Test-only fix: fire the abort synchronously in the read continuation that observes the tool-call part; the read fulfillment is queued before the refill pull, so the abort deterministically lands while the generator is suspended at the tool-call yield on all supported node versions. No product code changed.

Validation

• pnpm install, pnpm check (oxfmt + oxlint + typecheck ×4), pnpm -r build, pnpm -r test (agent 316, sandbox 191, all pass), pnpm publint, pnpm attw, actionlint: all green on node 26.8.1.
• Live e2e (dev.coder.com, temp token, expired after use): 1 passed / 6 failed — every failure is GET /api/experimental/chats/model-configs → 404 (Route not found). This is pre-existing platform drift, not caused by this PR: the identical suite on an origin/main worktree (442faed) with the same token fails identically (6 failed / 1 passed, same 404). The file upload/download round-trip test (no model resolution) passes on both.

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Generated with mux • Model: anthropic:claude-fable-5 • Thinking: xhigh

[ThomasK33]

@codex review

[ThomasK33]

@codex security review

[chatgpt-codex-connector]

Codex Review: Didn't find any major issues. Swish!

Reviewed commit: 836f0a2c56

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[chatgpt-codex-connector]

Security review completed. No security issues were found in this pull request.

Reviewed commit: 836f0a2c56

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