Fix race condition in doctor command provider check

The provider match check was running in parallel with provider
detection, causing intermittent failures where Docker was reported
as not installed even though it was.

Root cause:
- checkPrerequisites() and checkVvvInstallation() ran in parallel
- checkPrerequisites() populates ctx.availableProviders
- checkVvvInstallation() reads ctx.availableProviders
- Race condition: sometimes checkVvvInstallation() read before
  checkPrerequisites() wrote, seeing empty array

Fix:
- Run checkPrerequisites() first to populate ctx.availableProviders
- Then run checkVvvInstallation() and checkConfiguration() in parallel
- Both can now safely read ctx.availableProviders
- Maintains parallelization where possible

Impact:
- Consistent provider detection across all runs
- No more false "docker not installed" errors
- Still maintains good performance with partial parallelization

Author: tomjn

src/commands/doctor.ts

@@ -720,18 +720,22 @@ async function runAllChecks(vvvPath: string): Promise<CheckResult[]> {
   const results: CheckResult[] = [];
   let phaseStart: number;
 
-  // Phase 1: Run independent checks in parallel
+  // Phase 1: Prerequisites first (needed to populate ctx.availableProviders)
   phaseStart = Date.now();
   cli.info("Running initial checks...");
-  verbose("Running prerequisite, installation, and configuration checks in parallel...");
+  verbose("Checking prerequisites...");
 
-  const [prereqResults, vvvResults, configResults] = await Promise.all([
-    checkPrerequisites(ctx),
+  const prereqResults = await checkPrerequisites(ctx);
+  results.push(...prereqResults);
+
+  // Now run VVV installation and configuration checks in parallel (they can use ctx.availableProviders)
+  verbose("Checking VVV installation and configuration in parallel...");
+  const [vvvResults, configResults] = await Promise.all([
     checkVvvInstallation(ctx),
     checkConfiguration(ctx),
   ]);
 
-  results.push(...prereqResults, ...vvvResults, ...configResults);
+  results.push(...vvvResults, ...configResults);
   showPhaseProgress("Initial Checks", [...prereqResults, ...vvvResults, ...configResults], phaseStart);
 
   // Phase 2: VM State (determines if we can continue with VM-dependent checks)