feat(agents): add the UiPath Delegate SDK agent as a built-in harness [PILOT-7267]

[Mihaiii]

Issue

PILOT-7267

Summary

• Add DelegateSdkAgent (agent.type: delegate-sdk) as a built-in harness, moved from the internal coder_eval_uipath plugin: it drives UiPath Autopilot's Delegate agent through the @uipath/delegate-stdio Node host (JSON-Lines over stdio).
• AgentKind.DELEGATE_SDK + DelegateSdkAgentConfig (sdk_options, project_id, session_id), registered by register_builtins; empty delegate-sdk extra (the host is a Node package, like opencode).
• Layer-5 sdk_options override guard is now registry-driven: any kind whose config declares sdk_options qualifies (claude-code, delegate-sdk) — replaces the plugin's apply_overrides monkeypatch.
• Delegate-routed pricing rows (hyphenated ids: virtuoso-1-5, gpt-5-6-terra, kimi-k2-7-code, …) added to pricing.py and mirrored in evalboard/lib/pricing.ts, rates unchanged from the plugin.
• New docs/agents/DELEGATE_SDK.md; HARNESS_PARITY.md gains a delegate-sdk column; tasks/delegate_sdk_smoke_test.yaml.

Changes

Agent (src/coder_eval/agents/)

• delegate_sdk_agent.py + _delegate_s2s_token_file.py ported; get_environment_info spreads the base (CE046), system_prompt_semantics = "unknown".
• The plugin's logging bridge is gone: when DELEGATE_STDIO_VERBOSE forces tracing on a quiet run, host stderr is forwarded at INFO (DEBUG records would be dropped by the app handlers).
• Auth hint updated from the removed delegate-sdk login bin to npx @uipath/delegate-cli login.

Pricing caveat

• Rows carried over verbatim so the move is behavior-preserving. Several differ from the dotted rows for the same physical model (cache-write treatment); documented in pricing.py, deliberately not reconciled here.

Testing

• ruff format/check, make lint (389 passed), pyright (only the pre-existing missing-extra errors), ported suites + override/registry/pricing tests (343 passed); full suite green apart from pre-existing Windows/optional-extra failures.
• Pricing parity verified with a node mirror of pricing-parity.test.ts (no pnpm locally for vitest).
• Live host tests (-m live) not run.

Related PRs

• UiPath/coder_eval_uipath: https://github.com/UiPath/coder_eval_uipath/pull/110 — drops the plugin agent, nightly installs delegate-stdio from public npm
• UiPath/Autopilot: https://github.com/UiPath/Autopilot/pull/5582 — delegate-stdio 0.1.3 hardened for its first public npm release

Sequencing: this releases first (a feat → 0.12.0). The skills nightly pin and both PRs above depend on that version, and the nightly also needs @uipath/delegate-stdio published to npmjs (manual, not yet done).

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