Add PowerShell version logging for activation debugging (#851)

Implementing better PowerShell version logging for activation debugging
as requested in issue #706.

The issue stems from the PR review comment
(#693 (comment))
suggesting that logging PowerShell version information would be valuable
for debugging activation failures, especially given the differences
between Windows PowerShell 5.x and PowerShell 7+.

## Changes Made:
- [x] Analyze current PowerShell activation flow in pwshStartup.ts and
pwshEnvs.ts
- [x] Examine existing logging patterns and utilities
- [x] Test current build/compile state of project
- [x] Create utility function to detect PowerShell version via
`$PSVersionTable.PSVersion.Major`
- [x] Add PowerShell version logging to relevant activation code paths
- [x] Add version logging for both conda and non-conda activation
scenarios
- [x] Ensure logging follows existing patterns (traceInfo/traceVerbose)
- [x] Test changes and verify proper logging output
- [x] Use shorter -c flag instead of -Command for PowerShell commands

## Implementation Details:
1. **Added `getPowerShellVersion()` function** - Detects PowerShell
major version using `$PSVersionTable.PSVersion.Major` command with `-c`
flag
2. **Enhanced installation logging** - Now logs PowerShell version when
shells are detected (e.g., "SHELL: pwsh is installed (version 7)")
3. **Enhanced activation script error messages** - PowerShell errors now
include version info (e.g., "Failed to activate Python environment
(PowerShell 7): error details")

## Testing:
- All existing unit tests pass (128 passing)
- Code compiles successfully with no lint errors
- Manual testing confirms PowerShell version detection works correctly

These changes provide better diagnostic information for debugging
PowerShell activation issues without affecting existing functionality.

Fixes #706.

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Co-authored-by: copilot-swe-agent[bot] <[email protected]>
Co-authored-by: eleanorjboyd <[email protected]>

Author: Copilot

src/features/terminal/shells/pwsh/pwshStartup.ts

@@ -58,6 +58,27 @@ async function isPowerShellInstalled(shell: string): Promise<boolean> {
     }
 }
 
+/**
+ * Detects the major version of PowerShell by executing a version query command.
+ * This helps with debugging activation issues since PowerShell 5.x and 7+ have different behaviors.
+ * @param shell The PowerShell executable name ('powershell' for Windows PowerShell or 'pwsh' for PowerShell Core/7+)
+ * @returns Promise resolving to the major version number as a string, or undefined if detection fails
+ */
+async function getPowerShellVersion(shell: 'powershell' | 'pwsh'): Promise<string | undefined> {
+    try {
+        const command = `${shell} -c '\$PSVersionTable.PSVersion.Major'`;
+        const versionOutput = await runCommand(command);
+        if (versionOutput && !isNaN(Number(versionOutput))) {
+            return versionOutput;
+        }
+        traceVerbose(`Failed to parse PowerShell version from output: ${versionOutput}`);
+        return undefined;
+    } catch (err) {
+        traceVerbose(`Failed to get PowerShell version for ${shell}`, err);
+        return undefined;
+    }
+}
+
 async function getProfileForShell(shell: 'powershell' | 'pwsh'): Promise<string> {
     const cachedPath = getProfilePathCache(shell);
     if (cachedPath) {
@@ -125,7 +146,8 @@ function getActivationContent(): string {
         '        try {',
         `            Invoke-Expression $env:${POWERSHELL_ENV_KEY}`,
         '        } catch {',
-        `            Write-Error "Failed to activate Python environment: $_" -ErrorAction Continue`,
+        `            $psVersion = $PSVersionTable.PSVersion.Major`,
+        `            Write-Error "Failed to activate Python environment (PowerShell $psVersion): $_" -ErrorAction Continue`,
         '        }',
         '    }',
         '}',
@@ -220,6 +242,12 @@ export class PwshStartupProvider implements ShellStartupScriptProvider {
                     results.set(shell, this._isPs5Installed);
                 } else {
                     const isInstalled = await isPowerShellInstalled(shell);
+                    if (isInstalled) {
+                        // Log PowerShell version for debugging activation issues
+                        const version = await getPowerShellVersion(shell);
+                        const versionText = version ? ` (version ${version})` : ' (version unknown)';
+                        traceInfo(`SHELL: ${shell} is installed${versionText}`);
+                    }
                     if (shell === 'pwsh') {
                         this._isPwshInstalled = isInstalled;
                     } else {