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/projects.ts

@@ -22,6 +22,8 @@ export type Project = {
   deployBranch: string;
   /** Messaging channel for this project's group (e.g. "telegram", "whatsapp", "discord", "slack"). Stored at registration time. */
   channel?: string;
+  /** Issue tracker provider type (github or gitlab). Auto-detected at registration, stored for reuse. */
+  provider?: "github" | "gitlab";
   /** Project-level role execution: parallel (DEV+QA can run simultaneously) or sequential (only one role at a time). Default: parallel */
   roleExecution?: "parallel" | "sequential";
   maxDevWorkers?: number;