Refactor PythonResultResolver: Extract stateless handlers

[Copilot]

Separates stateful ID mappings from stateless payload processing in PythonResultResolver to improve maintainability and testability.

Architecture

PythonResultResolver (facade, per-workspace)
├── TestItemIndex (stateful, per-workspace)
│   └── runId ↔ vsId ↔ TestItem mappings
├── TestDiscoveryHandler (stateless singleton)
├── TestExecutionHandler (stateless singleton)
└── TestCoverageHandler (stateless singleton)

Changes

New components:

• testItemIndex.ts — Manages persistent ID mappings with validation and cleanup
• testDiscoveryHandler.ts — Processes discovery payloads, builds test tree
• testExecutionHandler.ts — Processes execution payloads, handles all outcome types
• testCoverageHandler.ts — Processes coverage payloads, creates FileCoverage objects

Interface changes:

• Added ITestIdMaps interface extracted from ITestResultResolver for cleaner handler signatures
• populateTestTree now takes ITestIdMaps instead of full resolver

PythonResultResolver updates:

• Now pure facade delegating to singleton handlers
• Exposes maps via getters for backward compatibility
• State limited to: testItemIndex, subTestStats, detailedCoverageMap

Usage

// Before: All logic in PythonResultResolver
resolver._resolveDiscovery(payload, token);

// After: Delegates to stateless handler
TestDiscoveryHandler.processDiscovery(
    payload,
    testController,
    testItemIndex,  // stateful component passed in
    workspaceUri,
    testProvider,
    token
);

Tests

• 32 new unit tests covering all extracted components
• All existing ResultResolver tests pass

Original prompt

execute this plan as described

Created from VS Code via the GitHub Pull Request extension.

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