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/services/tick.ts

@@ -162,7 +162,7 @@ export async function projectTick(opts: {
   const project = (await readProjects(workspaceDir)).projects[groupId];
   if (!project) return { pickups: [], skipped: [{ reason: `Project not found: ${groupId}` }] };
 
-  const provider = opts.provider ?? (await createProvider({ repo: project.repo })).provider;
+  const provider = opts.provider ?? (await createProvider({ repo: project.repo, provider: project.provider })).provider;
   const roleExecution = project.roleExecution ?? "parallel";
   const roles: Role[] = targetRole ? [targetRole] : getAllRoleIds() as Role[];