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/heartbeat.ts

@@ -304,7 +304,7 @@ async function performHealthPass(
   project: any,
   sessions: SessionLookup | null,
 ): Promise<number> {
-  const { provider } = await createProvider({ repo: project.repo });
+  const { provider } = await createProvider({ repo: project.repo, provider: project.provider });
   let fixedCount = 0;
 
   for (const role of getAllRoleIds()) {