feat: disable chmod in untrusted workspaces via workspace trust API

[jimeh]

Summary

• Previously the extension declared untrustedWorkspaces.supported: true, meaning chmod ran unconditionally — a malicious workspace could contain shebang files that silently become executable on save
• Switches to "supported": "limited" so the extension still loads in Restricted Mode but all permission changes are gated behind vscode.workspace.isTrusted
• Protects the permissionStrategy setting via restrictedConfigurations to prevent a workspace-level .vscode/settings.json from escalating to the "all" strategy

Changes

Runtime guard (src/document-handler.ts): Added !vscode.workspace.isTrusted early return in shouldSkipDocument(). This covers both the on-save handler and the manual command since both flow through processDocument(). No onDidGrantWorkspaceTrust event listener is needed — isTrusted is checked on every save, so granting trust mid-session immediately unblocks subsequent saves.

Manifest (package.json): Changed untrustedWorkspaces to "limited" with a user-facing description. Added restrictedConfigurations for permissionStrategy. Added isWorkspaceTrusted to the manual command's enablement clause to grey it out in the command palette when untrusted.

Tests (src/test/extension.test.ts): New workspace trust suite with 4 tests — untrusted blocks on-save, trusted works normally, manual command blocked when untrusted, and mid-session trust grant enables subsequent saves.

Test plan

• All 135 tests pass (including 4 new workspace trust tests)
• Compilation and linting clean
• Manual verification: open extension in untrusted workspace, save shebang file, confirm no chmod; grant trust, save again, confirm chmod works

🤖 Generated with Claude Code

[Copilot]

Pull request overview

This PR implements workspace trust support to prevent malicious files from becoming executable in untrusted workspaces. The extension now respects VS Code's workspace trust boundaries by blocking all chmod operations when vscode.workspace.isTrusted is false, addressing a security concern where opening an untrusted workspace containing shebang files could silently make them executable.

Changes:

• Added runtime workspace trust guard in shouldSkipDocument() to block chmod operations in untrusted workspaces
• Updated package.json manifest with untrustedWorkspaces.supported: "limited", restricted permissionStrategy configuration, and command enablement clause
• Added comprehensive test suite (4 tests) covering untrusted/trusted scenarios and mid-session trust grants

Reviewed changes

Copilot reviewed 4 out of 4 changed files in this pull request and generated no comments.

File	Description
src/document-handler.ts	Added !vscode.workspace.isTrusted check in shouldSkipDocument() to block all chmod operations in untrusted workspaces
package.json	Changed untrusted workspace support to "limited", added restrictedConfigurations for permissionStrategy, and updated command enablement with isWorkspaceTrusted context
src/test/extension.test.ts	Added workspace trust test suite with 4 tests covering untrusted blocking, trusted operation, manual command blocking, and mid-session trust grants
AGENTS.md	Documented workspace trust implementation pattern for future reference