Document unified Interactive Brokers Financial Advisor workflows - Feature 2624 fav2

[Farrell-A]

Summary

• Document fav2 enhancements, related brokerage account snapshots, asynchronous group assignments, and saved allocation updates.
• Update Interactive Brokers Financial Advisor routing and allocation-method guidance for unified and legacy modes.
• Document deployment configuration, Gateway desired-state behavior, freshness policy, limitations, and C#/Python examples.

This closes: QuantConnect/Documentation#2624
** This is part of a coordinated multi-repo feature release. See the attached files for thorough details**

User impact

Users can understand and safely use the new FAv2 account-state and group-management APIs, including asynchronous result polling, optimistic versioning, group-filter boundaries, and supported saved allocation methods.

Validation

• python3 doc_anchors.py — passed.
• python3 code-generators/detect-language-mixing.py — 0 language-mixing errors.
• url_check.py — 0 errors; 21 unrelated existing external-site warnings.
• PHP, JSON, sample-reference, mirrored-page, and git diff --check checks completed successfully while developing the documentation.
• Documentation behavior was reconciled against the exact four fa-v2 heads and the coordinated live-paper results.

Related PRs and sequencing

The coordinated PRs can be reviewed concurrently, but their release has package and platform dependencies:

1. Merge IBAutomater update and publish QuantConnect.IBAutomater 2.0.93.
2. Merge Lean update, which adds the brokerage-neutral FA contracts, default-safe LEAN configuration, and publish the corresponding LEAN packages.
3. Merge Lean.Brokerages.InteractiveBrokers update against the published IBAutomater and LEAN package surfaces.
4. Add the required deployment schema/UI inputs so Local Platform, LEAN CLI, direct cloud API, and QuantConnect Cloud deployments can emit the exact brokerage settings.
5. Publish this documentation update PR in alignment with the released implementations and deployment surface.
   The hosted deployment schema/UI must expose the unified-groups and group-management inputs under their exact brokerage-data keys. That platform work is external to this repository.

IBAutomater PR ──> publish 2.0.9X ───────────────┐
                                                 ├──> IB brokerage PR ─> brokerage release
LEAN PR ────────> publish LEAN 2.5.x packages ───┘                        │
                                                                          ├─> expose deployment inputs
Platform cloud schema/UI work (add 2 inputs)──────────────────────────────┘
                                                                          │
Documentation PR ─────────────────────────────────────────────────────────┘

Files attached explaining the full fav2 linked PR scope across repos, and testing conducted

fav2_live_verification_report.md
fav2_enhancement_summary.md
enhancement_change_inventory.md
enhancement_goals_findings.md
enhancement_scope.md
test_file_scope.md

Types of changes

• Bug fix (non-breaking change which fixes an issue)
• Refactor (non-breaking change which improves implementation)
• Performance (non-breaking change which improves performance. Please add associated performance test and results)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to change)
• Non-functional change (xml comments/documentation/etc)

Checklist:

• My code follows the code style of this project.
• I have read the CONTRIBUTING document.