docs(roadmap): add 2026 Q2 and H2 milestones

[sitabulaixizawaluduo]

Description

Add the 2026 Q2 (#1302) and 2026 H2 (#1381) milestone trackers to ROADMAP.md so
the file reflects the latest planning. Existing Q1 and historical sections are
preserved; "Last Updated" bumped to 2026-06-05.

Related Issue

Refs #1302, #1381

Type of Change

• Bug fix (non-breaking change that fixes an issue)
• New feature (non-breaking change that adds functionality)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)
• Documentation update
• Code refactoring (no functional changes)
• Performance improvement
• Test coverage improvement

Checklist

• I have read the Contributing Guide
• I have run formatting tools (pre-commit or manual)
• I have run relevant unit tests and they pass
• I have added tests for new functionality
• I have updated documentation if needed
• My branch is up to date with main
• This PR introduces breaking changes (if yes, fill out details below)
• If this PR changes documentation, I have built and previewed it locally with jb build docs
• No critical issues raised by AI reviewers (/gemini review)

Breaking Change Details (if applicable):

N/A

Additional Context

• Inserted in chronological order: H2 first, then Q2, then existing Q1.
• Rewrote bare URLs from [Roadmap] 2026 H2 Milestones #1381 source as inline issue/PR links (feat(mcore): add Bailing-MoE V2.5 megatron-bridge adapter #1372, feat(mcore): add GLM-5/DeepSeek-V3 model support (mbridge + megatron-bridge) #1373,
  [Feature] Operator CLI (areal) for the v2 microservice architecture #1374, [Feature] Migrate the primary megatron integration lib from mbridge to megatron-bridge #1260, [Feature] Support Audio model in the future #879, [Feature] Nightly experiments for performance validation #1284).

[gemini-code-assist]

Code Review

This pull request updates the project roadmap by adding detailed plans for 2026 Q2 and 2026 H2, covering backends, usability, and documentation. Feedback on these changes focuses on correcting typos and maintaining naming consistency, specifically changing 'Omini' to 'Omni', using 'DeepSeek-V3/V4' instead of 'dpsk-v3/v4', and correcting the casing of 'ArealOpenAI' to 'AReaLOpenAI'.

Important

The consumer version of Gemini Code Assist on GitHub is being sunset. Starting June 18, 2026, new organization installations will be blocked, and all code review activity will officially cease on July 17, 2026.
For more details on the timeline and next steps, please review the Help Documentation.

[TaoZex]

Does this mean introducing a new memory service to provide persistent memory across sessions and training iterations?