[WorkIQ] Add exact-item evidence retrieval for source-bound document workflows #93

Problem

The WorkIQ retrieve tool accepts natural-language search queries and may return multiple hits. The current result contract exposes source identity in retrievalHits[] (including webUrl and metadata), but document text is combined into one top-level markdown value. There is no documented per-hit body/snippet field or stable span/citation grammar that binds every body segment to exactly one hit.

An application processing a user-supplied OneDrive or SharePoint link can therefore prove which hit represents the requested item, but cannot safely isolate that item's text when the search returns additional hits. Passing the combined markdown to another model allows unrelated sources to influence the result.

Using the filename as the query is not a safe substitute: an exact filename diagnostic returned 15 hits. Passing a raw sharing URL as the natural-language query is also not a reliable supported contract.

Requested capability

Please provide either:

1. Per-hit bounded body/snippet content, with a documented stable source or citation-span mapping to the corresponding retrievalHits[] entry; or
2. A server-controlled exact-item semantic read operation accepting a OneDrive/SharePoint URL or resolved share/drive/item identity and returning evidence from only that item.

The capability should:

• Preserve sensitivity-label, DLP, extraction-rights and tenant policy enforcement.
• Avoid requiring clients to download the raw Office file.
• Provide deterministic source identity and a documented output contract.
• Support authenticated headless/non-interactive CLI workflows.
• Return explicit bounded error categories for authentication, access, policy and unsupported-content failures.

Security motivation

Without exact source-to-body binding, clients must either fail closed or risk unrelated-source contamination, prompt-injection influence and unverifiable evidence claims.

Environment

• WorkIQ plugin: 2.0.2
• GitHub Copilot CLI: 1.0.86-2
• Platform: Windows
• Interactive authentication and retrieve access succeeded; the limitation is the multi-hit source/body contract.

Related to #31 for non-interactive WorkIQ behavior, but this request is specifically about exact-item evidence isolation.