refactor(doctor): redesign with 3-tier output and consolidated checks

Consolidate 16 separate checks into 5 (system, config, providers, tools, models).
Add 3-tier formatting: default (problems-only), --status (dashboard), --verbose (deep diagnostics).
Read actual loaded plugin version from opencode cache directory.
Check environment variables for provider authentication.

src/cli/doctor/checks/model-resolution.test.ts

@@ -165,16 +165,4 @@ describe("model-resolution check", () => {
     })
   })
 
-  describe("getModelResolutionCheckDefinition", () => {
-    it("returns valid check definition", async () => {
-      const { getModelResolutionCheckDefinition } = await import("./model-resolution")
-
-      const def = getModelResolutionCheckDefinition()
-
-      expect(def.id).toBe("model-resolution")
-      expect(def.name).toBe("Model Resolution")
-      expect(def.category).toBe("configuration")
-      expect(typeof def.check).toBe("function")
-    })
-  })
 })