Fix get_direct_lake_sources failure when SQL endpoint source is referenced by name instead of GUID

[Copilot]

vertipaq_analyzer() and get_direct_lake_sources() raised a FabricHTTPException (400) when a Direct Lake model's SQL Analytics Endpoint source expression referenced the lakehouse/warehouse by its friendly display name (e.g. LH_Admin) rather than its GUID. The code passed this name straight through to metadata/artifacts/{artifact_id}, which only accepts GUIDs.

FabricHTTPException: 400 The request could not be processed due to missing or invalid information for url: 
https://.../metadata/artifacts/LH_Admin

Changes

• GUID detection: Check the artifact identifier extracted from the Sql.Database M expression with _is_valid_uuid before calling the artifacts API.
• Name resolution: When the identifier isn't a GUID, resolve it by matching the exact display name against the workspace's Lakehouses/Warehouses.
• Caching: The workspace item list is fetched once per get_direct_lake_sources() call and reused across all unresolved expressions to avoid redundant API calls.
• Ambiguity handling: If a name matches zero or multiple items, the source is skipped with a warning instead of silently resolving to the wrong item or crashing.

• Fixes Append Vertipaq Analyzer Error When Model Connected to Lakehouse SQL Analytics Endpoint #1258

[Copilot]

🟡 Changes recommended

Consumers must handle missing source descriptors or preserve an explicit failure.

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Pull request overview

Fixes Direct Lake source resolution when SQL expressions use lakehouse or warehouse names instead of GUIDs.

Changes:

• Detects GUID identifiers.
• Resolves friendly names by exact workspace-item matches.
• Caches workspace items per call.
• Warns and skips unresolved or ambiguous matches.

File summaries

File	Summary
src/sempy_labs/tom/_model.py	Adds name-based source resolution and caching; unresolved sources may cause incomplete results and downstream StopIteration failures.

Review details

• Files reviewed: 1/1 changed files
• Comments generated: 1
• Review effort level: Lite

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[Copilot]

Fixed in d3a0949: instead of skipping and returning a partial sources list, we now raise a ValueError when a Direct Lake expression's referenced item can't be resolved to exactly one Lakehouse/Warehouse, so callers like vertipaq_analyzer() never end up with a missing descriptor.