chore: upgrade vscode-languageclient to 10.1.2 - #1831

Compatibility follow-up for #1801:

The published vscode-languageclient 10.1.2 used by this PR enforces VS Code 1.91.0, not 1.110.0. Its npm manifest declares engines.vscode: ^1.91.0; its published runtime contains REQUIRED_VSCODE_VERSION = '^1.91.0' and throws below that version. I checked the installed artifact and the separately fetched published package. The runtime check rejects 1.90.0 and accepts 1.91.0 and 1.103.1.

This updates the dependency-floor finding in my earlier comment in #1801:

I temporarily lowered only vscode-R's manifest for an isolated VS Code 1.91.0 on macOS arm64 check, then restored it. With its bundled Node 20.9.0 / Electron 29.4.0 and R 4.6.1 / languageserver 0.3.20, both TCP and stdio passed checks for real client startup, source completion, signature help, multiple-range formatting, diagnostics after edits, and shutdown. The extension and its dependency declarations also type-check against the VS Code 1.91.0 API declarations. Node16 in this PR's tsconfig is a module-resolution setting; it does not set the extension-host Node requirement.

1.91.0 is therefore the enforced and tested language-client floor, but I am not claiming that the entire extension is fully validated there. A broader 1.91.0 extension-suite attempt encountered repeated timeouts in Interactive session/HTML export/list-view cases and was stopped; those need investigation before lowering the extension's supported baseline. The full tests passed at the versions already reported in this PR.

For the original OpenVSCode Server 1.103.1 use case, 1.103.1 exceeds the upgraded client's and R Syntax's requirements. This upgrade introduces no dependency requirement that would exclude it, but vscode-R's unchanged ^1.110.0 manifest still blocks installation. Lowering that manifest in a separately validated compatibility change would permit testing there; the actual OpenVSCode Server attach/session, plots, help, and Interactive behavior still need verification.

I recommend engines.vscode: "^1.94.0" as the minimum for the current extension plus the vscode-languageclient 10.1.2 upgrade. 1.94.0 is the earliest published VS Code release that passed all current VS Code tests in this local compatibility sweep. The published language client itself requires only 1.91.0; that dependency floor is lower than the full-suite baseline.

Results at commit b523f589b0682193eb0344d1e7340ff4faeff3cc, on macOS arm64 with R 4.6.1, R languageserver 0.3.20 and arf 0.5.3:

Every published release from the client's 1.91.0 floor through 1.93.1 was tested. Runs used fresh, private user profiles and only temporarily lowered the extension manifest so VS Code could load it. The final 1.94.0 run used the normal timeout settings, no bail, no retries, no test changes and no skips. It ran with bundled Node 20.16.0 / Electron 30.5.1, including the test that launches the actual VS Code host runtime with no standalone Node on PATH.

The first failure on all lower versions was Run Selection can create a persistent Interactive session and ordinary R exit leaves a restored notice: it timed out waiting for the stopped-session notebook notice after q("no") (test). On 1.91.1 this test passed in isolation but failed in the complete run, so the evidence establishes a current-suite compatibility boundary, not an inherent API requirement. Several later failures in the no-bail 1.93.0 run cascaded from Interactive timeouts.

The other current checks passed: 116 Node tests, 1,246 sess R assertions, the 6 source/bootstrap tests plus R source-identity/installer tests, typecheck, lint, build and VSIX identity verification. The source and dependency declarations also type-check against the actual VS Code 1.94.0 API with declaration checking enabled.

This updates discussion #1801: 1.110.0 is not necessary to pass the current tests on macOS, and VS Code desktop 1.103.1 passed the complete suites. OpenVSCode Server 1.103.1 exceeds the recommended 1.94.0 baseline and R Syntax's declared 1.90.0 minimum. The actual server environment and a 1.94.0 Linux/Windows matrix have not been tested here; the existing PR CI is green on all three OSes with its configured test versions.

The manifest remains ^1.110.0 in this PR. This is the validated recommendation for a subsequent minimum-version change, not a permanent manifest edit made during the sweep.