Add Multiagent Inventory static mock page, styles, scripts, and integration docs

[mobilbear]

Motivation

• Provide a Risk Management Platform (RMP)-consistent UI entry for Multiagent Feature Identification inventory so stakeholders can review page layout and flows before backend integration.
• Demonstrate the required filter bar, table, pagination, download actions, and feedback modal with the existing RMP look-and-feel and permission model.
• Supply backend design guidance including API pseudocode, SQL DDL, and example responses to accelerate server-side implementation.

Description

• Add multiagent_inventory/ with index.html, style.css, script.js, and README.md implementing a static mock of the inventory page, matching RMP styling and component patterns.
• Implement client-side filtering, sorting, pagination, download placeholders, and a feedback modal with role-based UI controls using a mocked currentUser and in-memory feedbackStore.
• Document backend endpoints (GET /api/multiagent/runs, GET /api/multiagent/files/{file_id}/download, POST /api/multiagent/runs/{run_id}/feedback), service pseudocode, and provide SQL DDL for MA_FILE, MA_RUN, and MA_FEEDBACK in README.md.
• Keep the New action feature-gated (disabled) and include recommended file naming, permission model, and integration notes for pre-signed downloads and audit logging.

Testing

• No automated tests were executed for this static mock change.

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Codex Task