copilot: remove leftover code from /tests test-generation codelens

[ulugbekna]

What

The "Generate tests using Copilot" codelens (and its companion testGenAction.ts) was removed in c0eaa94 (#3937), but its supporting infrastructure was left behind as dead code. This PR completes the cleanup.

Why

After c0eaa94:

• ITestGenInfoStorage.sourceFileToTest had no writers (the deleted testGenAction.ts was the only one), so every reader took the undefined branch.
• TreeSitterAST.getTestableNode / getTestableNodes and the underlying testableNodeQueries had no callers.
• Three large .spec.ts files tested only the now-orphaned parser API.

Changes

Deleted files

• extensions/copilot/src/extension/intents/node/testIntent/testInfoStorage.ts
• extensions/copilot/src/platform/parser/test/node/getTestableNode.{js,ts}.spec.ts + getTestableNode.util.ts
• extensions/copilot/src/platform/parser/test/node/getTestableNodes.ts.spec.ts + getTestableNodes.util.ts

Modified

• testFromTestInvocation.tsx: dropped the testGenInfo plumbing, simplified to the always-undefined path.
• test2Impl.tsx: dropped the unused srcFile?: ITestGenInfo prop and dead branch.
• Parser API (parserService.ts, parserServiceImpl.ts, parserImpl.ts, testGenParsing.ts, treeSitterQueries.ts): removed unused getTestableNode / getTestableNodes / TestableNode / testableNodeQueries.
• Service registrations (extension/services.ts, test/services.ts, simulationContext.ts): dropped ITestGenInfoStorage.

Preserved

• The /tests slash command and its TestsIntent, TestFromSrcInvocation, TestFromTestInvocation flows.
• _findLastTest and testInSuiteQueries — still used by testFromSrcInvocation.tsx.
• formatRequestAndUserQuery — still used by testFromSrcInvocation.tsx.

Validation

• npx tsgo --noEmit passes for tsconfig.json, test/simulation/workbench/tsconfig.json, and tsconfig.worker.json.
• All 80 tests in src/platform/parser pass (vitest --run).
• Pre-commit hygiene hook passes on the modified files.

Diff: 16 files changed, 11 insertions, 1145 deletions.

[Copilot]

Pull request overview

Removes leftover code from the previously deleted "Generate tests using Copilot" codelens. After the codelens was removed in c0eaa94, the supporting ITestGenInfoStorage had no writers and the parser's getTestableNode(s) / testableNodeQueries had no callers; this PR completes the cleanup while preserving the /tests slash command flow.

Changes:

• Deletes testInfoStorage.ts and all ITestGenInfoStorage service registrations; simplifies Test2Impl and TestFromTestInvocation to the always-undefined source-file path.
• Removes _getTestableNode / _getTestableNodes / TestableNode from the parser API (parserService.ts, parserServiceImpl.ts, parserImpl.ts, testGenParsing.ts) and drops testableNodeQueries from treeSitterQueries.ts.
• Deletes the three orphaned getTestableNode(s) spec files and their utility helpers.

Show a summary per file

File	Description
extensions/copilot/src/extension/intents/node/testIntent/testInfoStorage.ts	Deleted unused storage service.
extensions/copilot/src/extension/intents/node/testIntent/testFromTestInvocation.tsx	Removed dead testGenInfo plumbing and unused imports (IWorkspaceService, CodeBlock, formatRequestAndUserQuery).
extensions/copilot/src/extension/prompt/node/test2Impl.tsx	Dropped unused srcFile prop and dead branch.
extensions/copilot/src/extension/extension/vscode-node/services.ts	Removed ITestGenInfoStorage registration.
extensions/copilot/src/extension/test/vscode-node/services.ts	Removed ITestGenInfoStorage test registration.
extensions/copilot/test/base/simulationContext.ts	Removed ITestGenInfoStorage simulation registration.
extensions/copilot/src/platform/parser/node/parserService.ts	Removed getTestableNode(s) API.
extensions/copilot/src/platform/parser/node/parserServiceImpl.ts	Removed getTestableNode(s) wiring.
extensions/copilot/src/platform/parser/node/parserImpl.ts	Stopped re-exporting _getTestableNode(s).
extensions/copilot/src/platform/parser/node/testGenParsing.ts	Removed _getTestableNode(s) and TestableNode.
extensions/copilot/src/platform/parser/node/treeSitterQueries.ts	Removed testableNodeQueries.
extensions/copilot/src/platform/parser/test/node/getTestableNode.{js,ts}.spec.ts, getTestableNode.util.ts	Deleted orphaned tests/helpers.
extensions/copilot/src/platform/parser/test/node/getTestableNodes.ts.spec.ts, getTestableNodes.util.ts	Deleted orphaned tests/helpers.

Copilot's findings

• Files reviewed: 16/16 changed files
• Comments generated: 0