fix: persist issue tracker provider type in projects.json (#193) (#194)

Problem: Provider type (github/gitlab) was auto-detected on every
createProvider() call but never persisted, causing loss of
configuration after session restart.

Solution:
- Add 'provider' field to Project type
- Store detected provider type during project registration
- Pass stored provider type to createProvider() calls

Changes:
- lib/projects.ts: Add provider field to Project type
- lib/tools/project-register.ts: Save providerType to projects.json
- lib/tool-helpers.ts: Pass project.provider to createProvider
- lib/services/*.ts: Pass project.provider to createProvider

Impact: Issue tracker source now persists across restarts. Existing
projects will auto-detect on next use and should be re-registered or
manually edited to add provider field.

Fixes #193

lib/tool-helpers.ts

@@ -36,9 +36,10 @@ export async function resolveProject(
 
 /**
  * Create an issue provider for a project.
+ * Uses stored provider type from project config if available, otherwise auto-detects.
  */
 export async function resolveProvider(project: Project): Promise<ProviderWithType> {
-  return createProvider({ repo: project.repo });
+  return createProvider({ repo: project.repo, provider: project.provider });
 }
 
 /**