docs: add backlog wave orchestrator integration protocol and merge checklist

[akgohain]

Motivation

• Provide a lightweight, actionable protocol to integrate parallel cloud-task branches into feat/backlog-batch-1 with minimal cross-domain conflicts.
• Standardize merge ordering, conflict handling, and rebase behavior so merges can be executed in predictable waves (infra → backend → frontend).
• Ensure every merge wave has a repeatable verification gate with explicit pass/fail criteria to reduce regressions.

Description

• Added docs/dev/cloud-task-integration.md describing the Backlog Wave Orchestrator, branch roles, fixed merge wave order (low-risk infra first, backend second, frontend last), conflict classification and resolution priorities, escalation and documentation rules, and a 30-minute rebase timebox.
• Added docs/dev/merge-checklist.md containing the concrete command sequence for pre-wave sync, per-PR rebase, verification commands (including git status, Python compile check, and frontend lint/build), merge execution steps, and pass/fail criteria for each step.
• Included explicit rebase policy guidance to rebase onto feat/backlog-batch-1, resolve conflicts on the candidate branch, and use --force-with-lease only when necessary.
• Kept changes documentation-only and limited to the two files under docs/dev with no modifications to application code.

Testing

• Verified file creation and content by listing and printing files with nl and sed, and those inspections returned the expected content for docs/dev/cloud-task-integration.md and docs/dev/merge-checklist.md.
• Ran repository status checks (git status --short --branch) and committed the changes on branch agent/orchestrator-docs successfully.
• No automated unit/integration tests required for this docs-only change.

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Codex Task

[akgohain]

Consolidated into draft PR #165 (feat/codex-wave-integration). Closing this source draft to keep review in one place.