Run Windows and macOS tests weekly

[rcosta358]

Description

Closes #134.

Add weekly and manual Windows/macOS runs for client and server unit tests plus VS Code stable integration tests, with logs uploaded on failure. The diff contains only platform-tests.yml.

Related Issues

Depends on #146. The existing prerequisite PRs now form one chain through #145, #144, #143, #141, #142, #140, #139, #138, and #137 to main. The schedule becomes active when merged to the default branch.

Validation: 32 client tests, 24 server tests, lint, production/test TypeScript checks, and extension installation passed. Stable and minimum VS Code integration passed in PR CI. Fresh Windows/macOS validation passed on the final commit, including both unit-test suites and VS Code integration.

🤖 Generated with Codex

[CatarinaGamboa]

Base branch: this PR targets codex/phase-4-test-base, which has no PR to main and doesn't contain #139 (git merge-base --is-ancestor on #139's branch and phase-4: not an ancestor). Merging here won't get the weekly workflow onto main, and the schedule only runs from the default branch. Once the stack lands, this needs its base changed to main (or to the last PR in the stack), and it should be rebased onto a base that includes #139.

Reviewed with Claude Code (reviewer + adversarial agents per PR, findings checked against the code before posting).

[rcosta358]

Retargeted this PR onto #146, which leads through the stack to main, and merged #139 into the branch (939e85e). The description now lists the additional unit-test dependencies and notes that the schedule activates once it reaches the default branch. Client/server tests, stable integration, and full extension installation passed.

[CatarinaGamboa]

Most of the +4009 here is #139, #140, #141 and #142 merged in (vitest specs, server tests, publish.yml, ~2.5k lockfile lines), and #139/#140/#142 conflict with this stack in test.yml, package.json, tsconfig.json, .vscodeignore and package-lock.json. Could we land those into the chain first and rebase this down to just platform-tests.yml? Also, the linked Windows/macOS run predates these merges, so the server/vitest tests have not actually run on those OSes yet.

[rcosta358]

Addressed the oversized diff and outdated platform validation. Restacked the existing prerequisite PRs into the base chain, resolving the shared workflow/package/TypeScript conflicts; this PR now changes only platform-tests.yml (70 added lines).

Fresh Windows/macOS validation passed on final commit 7518175, including the client and server unit tests introduced by the prerequisite PRs. PR checks also passed both stable and minimum VS Code integration.

Independent review, 32 local client tests, 24 server tests, lint, both TypeScript checks, and full extension installation passed. The description now documents the actual dependency chain and current validation.