feat(coding-agents): add native DeepAgents Dcode integration

[Paritoshdagar]

Summary

• add a first-class DeepAgents Dcode Agent Plugin with Hooks V2, the shared skill, and a namespaced Hindsight MCP server
• parse Dcode transcripts and recover the final assistant message when the transcript lags the Stop event
• install through Dcode's native marketplace/plugin manager without patching ~/.deepagents or taking over foreign marketplace state
• keep the Dcode plugin version synchronized by the integration release script and document the harness

Verification

• 670 unit/integration tests passed
• package build and declarations passed
• real isolated dcode plugin marketplace add/install/uninstall smoke passed
• repository pre-commit hooks passed, including docs generation and lint
• targeted Prettier and git diff --check passed

Native contract

The root plugin.json is the Dcode boundary. It contributes hooks/hooks.json, skill/, and hindsight_* over stdio with HINDSIGHT_MCP_HARNESS=dcode; no config bridge, sync script, wrapper, or patched Dcode runtime is involved.

[strix-security]

Strix Security Review

No security issues found.

_{Updated for 508f86e.}

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Reviewed by Strix
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